Bring a large pot of salted water to a boil and cook the egg noodles according to the package directions. Drain and set aside.

Pat the swordfish steaks completely dry and season both sides generously with salt and pepper.

Heat the olive oil in a heavy skillet over medium-high heat until shimmering. Add the swordfish and sear for 4 to 5 minutes per side, until the surface is deeply golden and the center yields gently to a light press.

Transfer the swordfish to a plate and tent loosely with foil to rest.

Lower the heat to medium and melt 1 tablespoon of butter in the same skillet. Add the shallot and cook for 1 to 2 minutes, stirring often, until softened.

Pour in the grape juice or fish stock, scraping up the browned bits from the bottom of the pan, and let it simmer until reduced by about half, roughly 2 minutes.

Stir in the heavy cream and simmer for 3 to 4 minutes, until the sauce thickens enough to coat the back of a spoon.

Remove the pan from the heat and stir in the remaining tablespoon of butter, the chopped tarragon, and the lemon juice. Taste and adjust salt and pepper.

Toss the drained noodles directly in the sauce until well coated, then divide between bowls.

Slice the rested swordfish and lay it over the noodles, spooning any extra sauce on top. Finish with a scattering of fresh tarragon.