Stuffed Bell Peppers

1. Preheat oven to 375 degrees F. Line a large baking sheet with foil and spray it with nonstick spray.
2. Remove the tops of the peppers, core and seed them. Cut each bell pepper in half, lengthwise.
3. Place the cauliflower in the food processor. Process until it resembles rice.
4. Heat the olive oil in a large, deep skillet over medium-high heat, about 2 minutes. Add the riced cauliflower, the onion and the beef and cook, stirring and breaking the beef up as it cooks, about 7 minutes, until onion and cauliflower are soft, beef is lightly browned and liquids have evaporated. The mixture will not look very appetizing at this point. Don't worry about it, it will transform once you add the spices.
5. Add the garlic, salt, black pepper, chili powder, cumin, paprika and tomato paste. Cook 2 more minutes, stirring, until everything is well-blended. Remove from heat and stir in the cilantro.
6. Fill each bell pepper half with 1/10 of the mixture, packing it in, and place in the prepared baking sheet. Sprinkle with cheese, if using. Lightly spray with olive oil spray. Bake, uncovered, 30 minutes, until pepeprs are tender and cheese is melted. Remove from the baking sheet onto paper towels and let stand at least 10 minutes before serving.