To make the creamy spinach, wilt the washed and drained spinach in a large pan until wilted. Add the heavy cream, cheese, garlic powder, salt and pepper. Let it cool.
Cut each chicken breast horizontally, cutting a pocket into the breast without going all the way through.
Fill the pocket with about 1/3 cup of spinach filling. More if the breasts are larger.
Place 2 cups of keto-friendly tomato sauce into the bottom of an oven-safe dish. Place the stuffed breasts on top.
Dot the chicken breasts with the butter, and sprinkle with Parmesan cheese.
Bake at 375-F uncovered, for about 20 minutes, or until the breasts reach 165-F internally. You may need to adjust the cooking time if the breasts are larger or colder when you started, so keep an eye on them.
Serve and enjoy!
Notes
Tomato sauce nutritional info is not included in this recipe because I have no idea what sauce you might be using. Make sure it is sugar-free, and if possible, make your own tomato sauce!