01 - Pat the chicken breasts dry with paper towels and season both sides generously with salt and freshly ground black pepper.
02 - Heat the olive oil in a large skillet over medium-high heat. Add the chicken breasts and sear for 4–5 minutes per side until golden brown. Remove from the skillet and set aside on a plate.
03 - In the same skillet, add the diced onions and cook for 2–3 minutes until softened. Add the minced garlic and cook for another 30 seconds until fragrant.
04 - Add the halved cherry tomatoes and cook for 3 minutes, stirring occasionally, until they begin to release their juices and soften.
05 - Pour in the dry white wine, scraping up any browned bits from the bottom of the skillet. Bring to a simmer and let cook for 2 minutes to reduce slightly.
06 - Add the chicken broth, dried oregano, and crushed red pepper flakes if using. Stir to combine, then return the seared chicken breasts to the skillet.
07 - Cover the skillet with a lid and simmer on low heat for 12–15 minutes, until the chicken reaches an internal temperature of 165°F (74°C) and is fully cooked through.
08 - Remove the lid, stir in the chopped spinach, and cook for 1–2 minutes until just wilted. Taste the sauce and adjust seasonings with salt and pepper as needed.
09 - Serve hot, garnished with grated Parmesan cheese if desired. Pairs well with crusty bread or pasta.