Slice the peppers into half and remove the seeds, stems, and white parts. Drizzle the peppers with 1 tablespoon of olive oil and sprinkle over some salt and pepper to taste. Bake for 20 minutes.
While the peppers and roasting, heat the remaining olive oil in a large frying pan on a medium setting. Fry the onion until softened, about 5 minutes, then add the garlic and fry for another minute.
Add the ground beef and turn the heat up to medium-high. Break it apart with a wooden spoon, stirring as it cooks. Fry until browned.
Add the rice, tomatoes, spices, and some salt and pepper to taste. Stir well and cook for about another 5 minutes.
Once the peppers have finished in the oven, tip away any excess liquid that may have pooled inside them, then fill each pepper half with the beef mixture.
Sprinkle the grated cheese over the top of each pepper and return to the oven for another 12 minutes.