Pat the chicken thighs dry with paper towels. Season both sides with kosher salt, black pepper, smoked paprika, and garlic powder, pressing the spices into the meat so they adhere.

Prep vegetables

Peel and thinly slice the yellow onion. Core, seed and slice the red bell pepper into 1/2-inch strips. Cut the zucchini into 1/2-inch rounds or half-moons. Set vegetables aside.

Brown chicken

Heat a large deep skillet or sauté pan over medium-high heat. Add 2 tablespoons olive oil. When oil shimmers, add the chicken thighs in a single layer, skinless-side down (if any skin removed, just sear both sides). Sear without moving for 3–4 minutes until a deep golden crust forms, then flip and sear the other side 2–3 minutes. Remove chicken to a plate and set aside.

Sauce

Soften aromatics

Reduce heat to medium. Add the sliced onion to the same pan and a pinch more oil if the pan is dry. Cook, stirring occasionally, 4–5 minutes until translucent and starting to brown at the edges. Add the red bell pepper and zucchini and cook 3–4 minutes until slightly softened.

Build sauce

Stir in the tomato paste and cook 1 minute to remove raw flavor. Deglaze the pan with the white wine (if using), scraping up brown bits from the bottom. Add the tomato passata (or crushed tomatoes), chicken stock, red pepper flakes, dried oregano, bay leaf, and sugar. Stir to combine and bring to a gentle simmer.

Simmer with chicken

Return the seared chicken thighs to the pan, nestling them into the sauce so they are partially submerged. Reduce heat to low, cover partially, and simmer gently 18–22 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the sauce has thickened to your liking. Stir once midway to redistribute vegetables and sauce, being careful not to tear the chicken.

Adjust seasoning

Taste the sauce and add additional salt, pepper or a pinch more sugar if the tomatoes taste acidic. Remove and discard the bay leaf.

Finishing & Garnish

Finish

Stir in the fresh lemon juice and 1 teaspoon olive oil to brighten the sauce. Sprinkle chopped fresh parsley over the chicken. Let the dish rest 3–5 minutes off the heat to allow flavors to meld.

Serve

Serve the chicken thighs with sauce spooned over top alongside rice, pasta, or crusty bread to soak up the sauce.