Generously season the pounded flat chicken breasts with salt and pepper. Place side-by-side in a lightly sprayed baking dish.
In a bowl, combine the crushed tomatoes, Italian seasoning, parsley, and garlic. Add a few shakes of salt and pepper, taste, and adjust accordingly. If your tomatoes taste too acidic, you can add a little sugar, Swerve, or sugar substitute of your choice to counteract it. Just add a tiny bit (1/4 tsp) at a time and taste until it tastes right to you!
Pour the sauce over the chicken breasts and bake uncovered 25-35 minutes until the chicken is done.
Remove dish from oven and set the oven to Broil. Cover the top with the cheese and top with pepperoni. Broil until cheese is melted and pepperoni has crisped up a bit.