Bring a large pot of salted water to a rolling boil. Add the pasta and cook according to package instructions until al dente, about 8-10 minutes. Reserve ½ cup of pasta water, then drain the pasta and set aside.

Slice the chicken breasts into thin cutlets. Season with salt, pepper, and garlic powder. In a skillet, heat olive oil and butter over medium-high heat. Cook chicken for 5-6 minutes per side until golden brown and cooked through. Remove from skillet.

In the same skillet, add flour to the remaining oil and drippings. Cook for 1 minute. Gradually pour in chicken broth and then heavy cream, stirring well. Add pesto and lemon juice, simmer for 3-4 minutes to thicken.

Add sun-dried tomatoes, stirring until coated. Fold in baby spinach, stirring until wilted, about 2-3 minutes.

Add drained pasta to the skillet, mixing to coat well. Add reserved pasta water if necessary. Fold in sliced chicken.

Serve the pasta in individual plates. Optionally, sprinkle with Parmesan cheese.