Add olive oil and butter to a pan on medium heat. Add onion, jalapeño, diced bell pepper, celery, salt, pepper, Italian seasoning, red pepper flakes to the pan and cook to soften. Add garlic and cook for 1 minute. Remove to a large bowl and allow to cool down.

When the vegetables are cool add 3/4 of vegetables with the hamburger, rice, diced tomatoes, 3/4 cup of the cheese, and mix well.

Add tomato sauce, liquid from diced tomatoes can, and the remaining vegetables to an oven safe deep baking dish. Place the bell peppers, standing up in the dish, on top of the sauce. Fill each pepper with the beef mixture. Scoop some of the sauce and pour on top. Cover dish with aluminum foil and put in a 350°F oven.

Cook in oven for 90 minutes. Test peppers for doneness. They should be soft. Remove aluminum foil and scoop sauce up and pour over peppers. Next sprinkle the remaining cheese on top and put back in the oven uncovered for 15 minutes to melt cheese.