Preheat your oven to 375°F (190°C).

In a medium saucepan, combine 1 cup of uncooked brown rice with 2 cups of vegetable broth. Bring to a boil, then reduce heat to low, cover, and simmer for about 45 minutes until tender.

In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the diced onion and sauté for about 5 minutes until translucent.

Stir in the minced garlic, cumin, chili powder, smoked paprika, salt, and pepper. Cook for an additional 1-2 minutes.

Add the diced sweet potato and cook for 5-7 minutes until they soften.

Mix in the black beans, kidney beans, corn, bell pepper, and diced tomatoes. Heat through.

Fold in the cooked brown rice, stirring until combined.

Transfer the mixture into a greased 9x13-inch baking dish, spreading evenly.

Cover with aluminum foil and bake for 25 minutes.

Remove the foil and bake for an additional 15-20 minutes until sweet potatoes are tender and the top is golden.

Let the casserole cool for a few minutes before serving. Garnish with cilantro and serve with avocado slices and lime wedges.