Pound and season the chicken: Place the chicken between two sheets of parchment and pound to an even 1/2–3/4 inch thickness. Pat dry.
Season both sides with salt, pepper, garlic powder, onion powder, and Italian seasoning.
Sear the chicken: Heat olive oil in a large skillet over medium-high. Add chicken and sear 4–5 minutes per side, until golden and nearly cooked through. Transfer to a plate and tent with foil.
Sauté the garlic: Lower the heat to medium.
If the pan is dry, add a splash of oil. Add garlic and cook 30 seconds, stirring, until fragrant. Avoid browning.
Build the sauce base: Stir in tomato paste (if using).
Add chicken broth and stir, scraping up browned bits. Simmer 1–2 minutes to reduce slightly.
Make it creamy: Pour in milk, half-and-half, or cream. Stir in Parmesan and sun-dried tomatoes.
Add red pepper flakes if you like a little heat. Simmer on medium-low 2–3 minutes, until lightly thickened.
Finish the chicken: Return chicken and its juices to the pan. Spoon sauce over the pieces and simmer 3–5 minutes, until the chicken reaches an internal temperature of 165°F (74°C).
Brighten and serve: Stir in fresh basil and lemon juice.
Taste and adjust salt and pepper. Serve hot with your favorite sides.