Bring a large pot of salted water to a boil. Cook the pasta according to package directions. Reserve 1/2 cup pasta water before draining.
Pat the tilapia dry and season both sides with salt and pepper.
Heat the olive oil in a large skillet over medium-high heat until shimmering.
Add the tilapia and sear 2 to 3 minutes per side, until golden and just opaque throughout. Remove and set aside.
Reduce heat to low. In the same skillet, whisk together the pesto and heavy cream until smooth.
Add the drained pasta, tossing to coat. Add pasta water as needed to loosen the sauce.
Stir in the Parmesan and season with salt and pepper.
Divide the pasta among plates, top each with a tilapia fillet, and finish with tomatoes and basil.