Add the cherry tomatoes (cut in half) to the hot pan. Add in the roasted garlic cloves. Stir to combine.
Add in the peppers, onions, remaining ½ teaspoon sea salt and ¼ teaspoon black pepper. Stir and put the lid on. Reduce the heat to medium and let simmer until the tomatoes release their juice and the vegetables begin to soften to the texture you like.
Zest and juice the lemon (about 3-4 Tablespoons of lemon juice) and add to the pan.
Add the partially cooked chicken and stir. Place the spinach on top and put the lid on. Turn the heat down to low and let the spinach wilt.
When the spinach is wilted, check the internal temperature of the chicken to make sure it has reached at least 165°F/74°C. If it hasn't reached a safe internal temperature, turn the heat down to low and simmer until the chicken reaches 165°F/74°C.
Add in 2 Tablespoons of butter and stir to combine. This will thicken the sauce. If you want the sauce thicker, you can add a cornstarch slurry and bring to a simmer until thickened.
Serve over pasta, spaghetti squash, zucchini noodles, rice, or cauliflower rice.