Bring a large pot of salted water to a boil and cook the pasta according to package instructions until al dente; reserve 1 cup pasta water, then drain.

Slice the chicken breasts and season with salt, pepper, and garlic powder. Sauté in a skillet over medium-high heat with olive oil and butter for 5-6 minutes per side until cooked through.

In the same skillet, create a roux with flour. Gradually whisk in chicken broth and heavy cream, then simmer until thickened.

Stir in pesto and lemon juice, then add sun-dried tomatoes (if using) and cook for another 2 minutes.

Fold in spinach and stir until wilted, about 1-2 minutes.

Toss the cooked pasta with the sauce and adjust consistency with reserved pasta water if too thick.

Serve the pasta topped with sliced chicken and garnished with Parmesan cheese.