I got this recipe here and changed very little, and it was excellent!

Low carb stuffed peppers, my version
4 bell peppers (I used 1 orange, 1 red and 2 green)tops cut off, seeded and deveined
2T olive oil
2 large onions chopped
2 cloves garlic
1 1/2 (15 oz) cans chopped tomatoes with garlic, oregano and basil
1 tsp of paprika
1/4 tsp. each of red pepper flakes, chili powder, cayenne pepper and cumin
Salt and pepper to taste
1 lb. of ground sirloin (this really did make it taste better!)
2 c. shredded cheese (I used 1/2 Mexican blend and 1/2 mozzarella, but used quite a bit more, as I didn't pay attention and started to put it on to begin with)

Set a large pan on a med/high heat, when hot, add the oil, swirl and add the onions. Saute until they’re silky and translucent. Add the garlic and saute for another 2 minutes or so. Add the ground beef. When the beef is no longer raw, drain the fat if needed and then add the tomatoes and spices. Mix till cooked through and thoroughly blended.
Take off heat and set aside.

Pre-heat oven to 350º

Spray an oven safe dish with cooking spray and line your peppers up two by two. Spoon the ground beef into the peppers. I used two really large peppers and 2 medium ones and had quite a bit that I just put in the dish. Cook for 30 minutes, sprinkle with cheese and cook for 10 more minutes.

And here it is!