1. Preheat oven to 425°F; line a large, rimmed baking sheet with foil. Bring a large pot of water to a boil over high heat. Cut off stem end of each pepper, about 1/2 inch down, and use a tablespoon to scoop out seeds and membrane. If peppers don't sit upright, slice a sliver from bottom, being careful not to cut into the peppers, so they sit level while they bake.
2. Add peppers to pot and bring water back to a rapid boil. Cook until slightly softened, 8 to 10 minutes.
3. While peppers are cooking, warm 2 Tbsp. oil in a large skillet over medium-high heat. Add onion and sauté until softened, about 3 minutes. Add beef and cook, stirring, until crumbled and no longer pink, about 3 minutes. Add tomatoes, cinnamon, cloves and rice. Stir until almost all liquid is absorbed, about 3 minutes. Season with salt and pepper. You should have about 4 cups filling.
4. Using tongs, remove peppers from water and drain, inverted, on paper towels. Pack each pepper with about 1 cup filling. Arrange peppers on baking sheet, sprinkle with bread crumbs and drizzle with remaining 2 Tbsp. oil. Bake until browned, about 15 minutes.