01 - Pat the chicken breasts dry with paper towels and season both sides generously with kosher salt and freshly ground black pepper.
02 - Heat the olive oil in a large skillet over medium-high heat. Sear the chicken breasts for 4–5 minutes per side until a deep golden crust forms. Transfer to a plate and set aside.
03 - In the same skillet, cook the diced onion for 2–3 minutes until softened and translucent. Add the minced garlic and stir for 30 seconds until fragrant.
04 - Add the halved cherry tomatoes to the skillet and cook for approximately 3 minutes, allowing them to release their natural juices and begin to 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 the liquid reduce for 2 minutes.
06 - Stir in the chicken broth, dried oregano, and crushed red pepper flakes. Nestle the seared chicken breasts back into the skillet.
07 - Cover the skillet with a lid and reduce the heat to low. Simmer gently for 12–15 minutes until the chicken reaches an internal temperature of 165°F.
08 - Remove the lid, stir in the chopped spinach, and cook for 1–2 minutes until just wilted and vibrant green.
09 - Taste the sauce and adjust the salt and pepper as needed. Serve immediately, garnished with freshly grated Parmesan cheese if desired.