Season the chicken: Pat the chicken dry. Toss with salt, black pepper, Italian seasoning, and garlic powder until evenly coated.
Cook the pasta: Bring a large pot of salted water to a boil.
Cook pasta until al dente according to package directions. Reserve 1/2 cup pasta water, then drain.
Brown the chicken: In a large skillet over medium-high heat, add 1 tablespoon olive oil and 1 tablespoon butter. When hot and foamy, add chicken in a single layer.
Sear 3–4 minutes per side until golden and cooked through. Transfer to a plate and cover loosely.
Sauté the veggies: In the same skillet, add remaining 1 tablespoon olive oil. Add bell peppers and red onion with a pinch of salt.
Cook 4–5 minutes, stirring occasionally, until slightly softened and lightly charred in spots.
Add the garlic and heat: Reduce heat to medium. Stir in garlic and red pepper flakes (if using). Cook 30–60 seconds until fragrant.
Don’t let the garlic brown.
Deglaze and build the sauce: Pour in white wine and scrape up any browned bits. Simmer 1–2 minutes to reduce slightly. Add 3/4 cup chicken broth, 2 tablespoons butter, lemon zest, and lemon juice.
Simmer 2–3 minutes to let the flavors meld.
Combine everything: Return chicken and any juices to the skillet. Add the drained pasta and Parmesan. Toss until coated.
If the sauce seems dry, add splashes of reserved pasta water until silky and glossy.
Finish and serve: Taste and adjust with more salt, pepper, or lemon juice. Sprinkle with parsley. Serve hot with extra Parmesan and lemon wedges.