Preheat the oven to 400°F and line a baking sheet with parchment paper.

Slice the peppers in half lengthwise and remove the seeds and ribbing. Place on the baking sheet, drizzle with olive oil and sprinkle with salt and pepper, and roast cut side up for 15 minutes.

In a large skillet, heat 1 tablespoon olive oil over medium heat. Add the onion, cauliflower, red pepper, cumin, coriander, oregano, garlic, 1/2 teaspoon salt, and several grinds of black pepper. Cook until the onion is soft and the cauliflower is lightly browned, about 5 to 8 minutes.

Remove from the heat and stir in the black beans, rice, spinach, lime juice, and tomatillo salsa. Taste and adjust seasonings.

Scoop the filling into the peppers and top with the cheese, if desired. Bake for 15 to 30 minutes, or until the filling is heated through and/or the cheese is melted, if using. If desired, turn on the broiler for a few minutes to brown the cheese on top.

Serve with avocado slices, cilantro, tomatillo salsa, cilantro lime crema, and lime slices on the side.