Place oven rack to middle of the oven and heat oven to 400 F. Pour tomato sauce in the bottom of a 13x9 baking pan.
Pat chicken breast with a paper towel to dry. Season both sides with salt & pepper. Coat each side with grated parmesan cheese, pressing into the chicken for it to adhere.
Place chicken in tomato sauce and bake in oven for 10-15 minutes (depending upon thickness of chicken).
Pull chicken out of the oven and divide shredded cheese evenly between chicken breast; spreading on the top of each. Place 5 turkey pepperoni on each chicken breast. Turn oven up to 425 and place back in oven.
Bake for 7 minutes for cheese to melt. Let cool slightly and serve.