Preheat your oven to 375°F (190°C).
- Slice the zucchini in half lengthwise. Using a spoon, scoop out the center of each zucchini half to create a hollow “boat,” leaving about 1/4-inch of zucchini around the edges. Set the scooped-out zucchini aside for later.
- Place the zucchini boats on a baking sheet, drizzle them with a little olive oil, and sprinkle with salt and pepper. Roast in the preheated oven for about 10-12 minutes until the zucchini is slightly tender but still firm.
- While the zucchini is roasting, heat olive oil in a large skillet over medium heat. Add the ground beef and cook until browned, breaking it up with a spatula.
- Add the chopped onion and bell pepper to the skillet with the beef. Cook for 2-3 minutes until the vegetables are softened.
- Stir in the minced garlic, ground cumin, smoked paprika, oregano, and chili powder (if using). Cook for another minute until fragrant.
- Add the diced tomatoes (with juice) to the skillet and stir in the cooked rice. Let the mixture simmer for 5-7 minutes, allowing the flavors to meld together. Taste and adjust seasoning with salt and pepper as needed.
- Remove the zucchini boats from the oven and spoon the beef and rice mixture into each boat, packing the filling in tightly.
- Sprinkle shredded cheese over the stuffed zucchini boats and return to the oven. Bake for an additional 10-15 minutes, or until the cheese is melted and bubbly.
- Garnish with fresh cilantro or parsley before serving, if desired.