Preheat the oven to 400°F and line a baking sheet with parchment pepper. Slice the peppers in half and remove the seeds and ribbing. Place on the baking sheet, drizzle with olive oil and pinches of salt and pepper, and roast cut side up for 15 minutes.
In a large skillet, heat the olive oil over medium heat. Add the onion, cauliflower, red pepper, cumin, coriander, oregano, garlic and a pinch of salt and 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 bake for 15 minutes.
Serve with the avocado, cilantro, tomatillo salsa, green chile cashew cream and lime slices on the side.