Preheat oven to 350°F.

Cut the tops off the peppers and remove all the seeds and white stuff. Simmer peppers in boiling water for 5 minutes

Heat olive oil in large skillet over medium heat. Stir in onions, garlic and diced tomato and fry for about 3 minutes. Stir in ground beef. Cook the meat until it is no longer pink.

Stuff the mixture into the hollowed-out peppers. Place stuffed peppers onto a baking tray

Bake in preheated oven for 12-15 minutes. Top with cheddar cheese and bake for 5 additional minutes.