Season the chicken. Pat the chicken dry.
Season both sides with salt and black pepper. This helps the sear and builds flavor from the start.
Warm the pan. Heat the olive oil in a large skillet or Dutch oven over medium-high heat until it shimmers. You want it hot enough to brown quickly.
Sear the chicken. Add the chicken in a single layer.
Sear 3–4 minutes per side until golden. It doesn’t need to be cooked through yet. Transfer to a plate.
Soften the aromatics. Lower the heat to medium.
Add the onion with a pinch of salt. Cook 4–5 minutes until translucent. Stir in the garlic and red pepper flakes; cook 30 seconds until fragrant.
Build the base. Add the tomato paste and cook 1 minute, stirring to coat the onions.
This step deepens the tomato flavor.
Add tomatoes and herbs. Pour in the crushed tomatoes and chicken broth. Stir in oregano, dried basil, and sugar if using. Taste and season with salt and pepper.
Simmer gently. Return the chicken and any juices to the pan, nestling it into the sauce.
Reduce heat to low and simmer uncovered for 15–20 minutes, flipping once, until the chicken is cooked through and tender.
Finish the sauce. Stir in the butter for richness, if using. If you have fresh basil, add it now. Adjust seasoning—more salt, pepper, or a pinch of sugar if the tomatoes are sharp.
Serve. Spoon the chicken and sauce over pasta, rice, or polenta, or serve with crusty bread.
Top with chopped parsley or basil and a light shower of Parmesan.