Bring a large pot of salted water to a rolling boil. Add pasta and cook according to package directions until al dente, about 8–10 minutes. Reserve ½ cup of pasta water before draining.

Season chicken breasts with garlic powder, salt, and pepper. In a skillet, heat olive oil and butter over medium-high heat. Cook chicken for 5-6 minutes per side until golden brown. Transfer to a plate to rest before slicing.

In the same skillet, lower heat and sprinkle in flour. Cook for about 1 minute to form a roux, stirring constantly until golden.

Gradually pour in chicken broth while stirring to combine. Scrape up browned bits and allow to simmer gently for 2-3 minutes until slightly thickened.

Stir in heavy cream, pesto, and lemon juice. Mix well, then add sun-dried tomatoes and simmer for another 2-3 minutes until smooth.

Add spinach to the creamy sauce and cook until wilted, about 1-2 minutes.

Add drained pasta to the skillet. Toss to coat the pasta with sauce, adding reserved pasta water as needed to adjust consistency.

Slice the rested chicken and arrange it over the pasta. Optionally, sprinkle with Parmesan cheese before serving.