Bring a large pot of salted water to a rolling boil. Add pasta and cook until al dente, about 8–10 minutes. Reserve ½ cup of pasta water, then drain pasta.

Season chicken breasts with garlic powder, salt, and pepper. In a skillet, heat olive oil and butter. Cook chicken for 5–6 minutes per side until golden brown and internal temperature reaches 165°F. Remove, let rest, and slice.

In the same skillet, add flour and stir for 1 minute to create a roux.

Gradually whisk in chicken broth, stirring continuously. Add heavy cream, pesto, and lemon juice. Stir in sun-dried tomatoes and let simmer for 3–4 minutes.

Add spinach and cook until wilted, about 2 minutes.

Add drained pasta to skillet, tossing to coat in sauce. Add reserved pasta water if the sauce is too thick.

Fold in sliced chicken and serve immediately, garnished with Parmesan if desired.