Preheat oven to 375 degrees.
Coat a baking dish with a little coconut oil. In a food processor, combine the first 6 ingredients (cauliflower through black pepper); pulse until roughly combined and cauliflower is of a minced consistency.
Melt the coconut oil in a large skillet over medium-high heat. Add onion and ground beef and cook until beef is browned.
Add cauliflower mixture and toss for a few seconds.
Stuff bell peppers with cauliflower/beef mixture and place in prepared baking dish; bake for about 30 minutes.