Cook the penne pasta according to package instructions in salted boiling water. Reserve 1 cup of pasta water before draining and set aside.

Pat salmon fillets dry, season with salt and pepper, and sear in a skillet with olive oil for 3 minutes per side until golden and cooked through. Chop into bite-sized pieces.

In the same skillet, add more olive oil and butter, sauté one minced onion until translucent, then toss in halved cherry tomatoes and cook until they start to burst.

Reduce heat, pour in heavy cream, mix in reserved pasta water, and stir in pesto until the sauce is creamy and well combined.

Add the drained penne pasta and chopped salmon to the skillet, tossing gently until coated with the sauce, adjusting with more pasta water as needed.

Squeeze lemon juice over the pasta, stir to mix, and serve warm.