Directions

1. Preheat oven to 350ºF.
2. Slice off the stem ends of 4 bell peppers. Cut the flesh from the stem and chop. You should have about 1 cup. Scoop out seeds from the pepper cavities. Bring about an inch of water to a boil in a large pot fitted with a steamer basket. Steam the peppers until they start to soften, about 3 minutes. Remove the peppers from the pot and set aside.
3. Pulse 2 cups cauliflower in a food processor until broken down into rice-size pieces. Heat 1 tablespoon oil in a large skillet over medium heat. Add the cauliflower rice and a pinch each of salt and pepper. Cook, stirring, until softened and starting to brown, about 3 minutes. Transfer to a small bowl.
4. Wipe out the pan. Add the remaining 1 tablespoon oil, the chopped bell pepper and ½ cup onion. Cook, stirring, until starting to soften, about 3 minutes. Add 1 pound beef, 2 cloves garlic, ½ teaspoon oregano and the remaining ½ teaspoon salt and ¼ teaspoon pepper. Cook, stirring and breaking up the beef with a wooden spoon just until no longer pink, about 5 minutes. Add 8 ounces tomato sauce and the cauliflower rice; stir to coat.
5. Place the peppers upright in an 8-inch-square baking dish. Fill each pepper with a generous 1 cup of the cauliflower rice mixture. Top each pepper with 2 tablespoons cheese.
6. Bake until the filling is heated through and the cheese is melted, 20 to 25 minutes.