There's something to be said about an old classic. I use ground turkey in my recipe for a lighter version.
Ingredients

6 red bell peppers seeded, stems removed and bottoms flattened
2 cups of cooked rice (white or brown)
1/2 tbsp of vegetable oil
500g of ground turkey
1 large onion diced
3 cloves of garlic minced
680 ml bottle (about 3 cups) of tomato puree
1 tbsp of dried oregano
1 1/2 cups of freshly grated parmesan cheese
Salt and pepper to taste
Instructions
Preheat oven to 400 degrees
Sautee onions and garlic in oil
Add ground turkey and cook until juices run clean (about 7-8 minutes)
Add tomato puree, rice and cheese
Season with oregano, salt and pepper
Fill each pepper with rice mixture
Bake for 40-45 minutes