4 slices mozzarella
4 bell peppers, cored and halved
15 oz. marinara
2 tbsp. olive oil, divided
1/2 tsp. red pepper flakes
1 tsp. kosher salt
2 cloves garlic
1 egg
1/4 cup grated Parmesan
1/4 cup chopped parsley
1/3 cup bread crumbs
1 pound ground beef