Tonnato Sauce with Sliced Beef

Fan the beef thin enough and it goes translucent at the edges, pink shading toward rose where the light comes through. Spoon the sauce over it and watch how the pale, oily beige pools into the gaps between slices before you even pick up a knife — it doesn’t sit on top of the meat so much as settle into it. That’s the whole mechanism of Tonnato Sauce with Sliced Beef: a cold, savory sauce built from tuna, anchovy, and capers, draped over meat sliced thin enough to disappear under it.

This is the beef version of vitello tonnato, the northern Italian dish traditionally made with veal. Swap in beef — specifically a cut you can roast, chill, and slice paper-thin — and the pairing holds up just as well, maybe better, with a slightly deeper, more mineral flavor standing up to the sauce’s brine and fat.

What Makes It Worth Your Time

This is a make-ahead dish disguised as a dinner-party centerpiece. The beef needs to chill fully before you can slice it thin, and the sauce actually improves after a few hours in the refrigerator, which means most of the real work happens the day before and what’s left on the night itself is assembly. Few dishes look this considered while asking this little of you in the moment.

It’s also a genuinely useful dish to have in rotation for warm weather, since nothing about it involves turning on the oven for longer than it takes to roast a small piece of beef, and nothing about it is served hot. If you’ve only ever thought of tuna and beef as separate categories of protein that don’t belong on the same plate, this is the dish that resolves that — anchovy and capers do the bridging work, giving the sauce enough salt and acid to read as a savory condiment rather than a seafood dish sitting next to red meat.

What You’ll Need

For the Beef

• 2 lb beef eye of round or tenderloin, tied if using round — a lean, tight-grained cut is what allows the wafer-thin slicing this dish depends on; a fattier or looser-grained cut will tear instead of shaving cleanly
• 1 tablespoon olive oil
• Kosher salt and freshly cracked black pepper
• 2 cups beef broth
• 1 bay leaf
• 1 tablespoon red wine vinegar (a stand-in for the dry white wine traditional versions poach the meat in — it adds the same brightening acidity without the alcohol)

For the Tonnato Sauce

• 1 can (5 oz) oil-packed tuna, drained
• 3 anchovy fillets — these disappear into the sauce and don’t read as fishy on their own; they’re doing the same work MSG or fish sauce does in other cuisines, deepening savoriness without announcing themselves
• 2 tablespoons capers, rinsed, plus extra whole capers for garnish
• 3/4 cup mayonnaise
• 2 tablespoons fresh lemon juice
• 2–4 tablespoons of the reserved beef poaching liquid, to thin
• Freshly cracked black pepper
• Fresh parsley or chives, chopped, for garnish

No anchovies in the pantry? A teaspoon of fish sauce gets you close, though you’ll lose some of the anchovy’s distinct saline character. Skip it entirely and the sauce turns flatter — noticeably less savory — since the anchovies are one of the few ingredients here doing real structural work rather than just flavor.

Making It

1. Sear the beef. Pat the beef dry and season generously with salt and pepper. Heat the olive oil in a heavy pot over high heat until it shimmers, then sear the beef on all sides, about 2 minutes per side, until it’s a deep, even brown all around — no gray patches. You’ll hear a sharp, steady sizzle the whole time; if it goes quiet, your pan has lost heat and needs a minute to recover before you keep going.
2. Poach gently. Add the beef broth, bay leaf, and vinegar to the pot — the liquid should come about two-thirds up the sides of the beef, not fully submerge it. Bring to a bare simmer, cover, and cook for 18–22 minutes for medium-rare, until an instant-read thermometer reads 125°F (52°C) at the thickest point. The liquid should stay at a gentle murmur throughout, just the occasional bubble breaking the surface — a hard simmer will toughen the outer layer before the center catches up.
3. Cool, then chill completely. Remove the beef from the poaching liquid and let it rest at room temperature for 15 minutes, then wrap tightly in plastic and refrigerate for at least 4 hours, ideally overnight. Reserve the poaching liquid — strained and cooled, it becomes the thinning agent for the sauce. Skipping the full chill is the single biggest reason this dish goes wrong: warm beef simply will not slice thin enough.
4. Make the sauce. In a food processor, combine the tuna, anchovies, and capers and pulse until roughly broken down. Add the mayonnaise and lemon juice and process until smooth — the color should shift from the mayonnaise’s pale yellow to a slightly gray-beige, and the texture should look like a loose, pourable aioli. Thin with the reserved poaching liquid, a tablespoon at a time, until the sauce coats the back of a spoon but still moves when tilted. Taste and adjust with black pepper; it likely won’t need more salt, since the anchovies and capers carry plenty.
5. Slice thin. Using a sharp knife or a mandoline, slice the chilled beef against the grain as thin as you can manage — close to translucent. Cold meat is what makes this possible; even a partially warm center will make clean, thin slices difficult.
6. Plate and sauce. Lay the beef slices, slightly overlapping, across a large platter. Spoon the tonnato sauce over the top in loose ribbons rather than one solid layer — you want streaks of beef still visible through the sauce. Scatter with whole capers and fresh herbs.

The Details That Separate Good from Great

The thickness of the beef is not a minor detail — it’s the entire architecture of the dish. Slices that are too thick eat like a beef dish with sauce on the side; slices this thin let the meat and sauce function as one bite, which is the actual intention. If you don’t own a mandoline, freeze the beef for 20–30 minutes after its full chill — not solid, just firm enough to give your knife more control.

The sauce’s consistency matters more than most people assume. Too thick, and it sits on the meat like a paste, clumping instead of draping. Too thin, and it pools uselessly at the edges of the platter. The reserved poaching liquid is the right thinning agent — not water, not more lemon juice — because it carries a little of the beef’s own savoriness back into the sauce, tying the two components together instead of diluting them apart.

Let the sauced platter sit in the refrigerator for at least 20 minutes before serving. The sauce needs a little time to settle into the gaps between slices rather than sitting on the surface — that resting period is what makes the finished dish look composed instead of just assembled.

Where It Goes Wrong

Slicing warm beef is the most common failure, and it’s an easy one to fall into if you’re impatient — the beef looks cool to the touch well before it’s chilled all the way through. Give it the full four hours. If you’re in a genuine hurry, slice thicker rather than tearing thin slices out of meat that isn’t ready; a slightly thicker cut still works, a torn one doesn’t.

Overcooking the beef past medium-rare is the second failure, and it’s less forgiving than it sounds. Beef cooked past that point turns gray and loses the moisture that makes thin slices taste tender rather than dry — and because this dish serves the beef cold, any dryness in the meat becomes more obvious than it would in a hot dish, where fat and juices are still actively moving. Pull the beef at 125°F and trust that carryover heat during the rest will bring it the rest of the way.

Oversaucing is the quieter mistake. Drown the beef in tonnato and you lose the visual and textural point of the dish entirely — it stops reading as sliced beef with sauce and starts reading as beef submerged in dip. Spoon it on, then stop before your instinct tells you to add more.

Ways to Make It Your Own

Pork tenderloin makes a genuinely good substitute for the beef — leaner and milder, it lets the sauce take a more dominant role, which suits people who find the classic pairing a little heavy. If you want more texture in the sauce itself, fold in a tablespoon of finely diced cornichon after processing rather than blending it in, so you get small pops of acidity between bites instead of a uniformly smooth sauce. For a version with more heat, whisk a small spoonful of prepared horseradish into the finished sauce — it cuts through the richness of the mayonnaise and gives the dish a sharper finish without overwhelming the tuna and anchovy base.

Putting It on the Table

Serve this as a starter for a warm-weather dinner, plated on a large platter for the table to share, with a stack of small plates. Arugula tossed with lemon and olive oil makes a natural bed underneath or alongside the beef, its peppery bite standing up to the sauce’s richness. A simple crusty bread on the side is useful for anyone who wants to mop up extra sauce once the beef is gone. Keep other dishes on the table light — a plate of roasted vegetables or a simple grain salad — since the tonnato sauce is rich enough to carry the meal on its own without heavy competition.

Keeping and Reheating

This dish is served cold, so there’s no reheating step to worry about — only storage. Keep the beef and sauce in separate airtight containers in the refrigerator; sliced beef stored under sauce for more than a day tends to take on a slightly mushy texture where the acid in the sauce has started to break down the surface of the meat. Stored this way, both components hold well for up to 3 days. Assemble the platter fresh each time you serve it rather than storing it pre-sauced. The sauce itself, kept separately, actually improves over the first 24 hours as the anchovy and caper flavors settle and round out.

Approximate Nutrition Per Serving

Values are estimates for informational purposes only and will vary based on specific ingredients and portion sizes.

A Last Word

There’s something particular about a dish that asks you to trust an unlikely pairing and rewards you for it — tuna and beef have no business working together on paper, and yet the sauce’s brine and the meat’s quiet richness meet somewhere in the middle that neither could reach alone. Make it once, slice it thin, and the logic stops needing an explanation. It just makes sense on the plate, which is the only proof a dish like this ever really needs.