Bring a large pot of salted water to a rapid boil. Cook pasta according to package directions until al dente, about 8–10 minutes. Reserve ½ cup pasta water, drain, and set aside.

Season sliced chicken with garlic powder, salt, and pepper. In a skillet, heat olive oil and butter over medium heat. Cook chicken for 5–6 minutes on each side until golden and cooked through. Transfer to a plate and rest.

In the same skillet, sprinkle flour, stirring constantly for about 1 minute to thicken the sauce, scraping up pan bits.

Gradually pour in chicken broth, stirring to combine. Then add heavy cream, pesto, lemon juice, and sun-dried tomatoes. Simmer for 3–5 minutes until thickened.

Lower heat and add fresh baby spinach, stirring until wilted, about 2 minutes.

Add drained pasta to the skillet, tossing to coat in the creamy sauce. Use reserved pasta water as needed to adjust consistency.

Slice rested chicken and add back to the pasta mixture. Serve hot, garnished with freshly grated Parmesan cheese if desired.