Cut the tops of the peppers, and with a long skinny knife remove the membrane and seeds
Dice the pepper tops and add them to the diced onions
over medium-high heat, sautee the onions and pepper tops until the onions are translucent
Add the garlic, Italian seasoning, and red pepper flakes
remove from heat and set aside
In a bowl, add the sausage, cheeses, egg, and onion mixture
Mix until well combined
Place sausage mixture in a piping bag and pipe the mixture into the peppers making sure the peppers are completely filled
In a large casserole dish, cover the bottom with half of the sauce
Lay the pepper out in a single row and top with the remaining sauce
Cover with foil and place in a 375 oven for 30 minutes
Remove from the oven and remove the foil
Top with the reserved parmesan and mozzarella cheese
Place back in the oven for 15 more minutes
Makes a nice dinner served with side salad