In a large pot or Dutch oven, heat a drizzle of oil over medium heat. Add the diced yellow onion and green bell pepper. Sauté for about 5 minutes, or until they become soft and translucent. Add the minced garlic and cook for another minute, stirring frequently to prevent burning.
Chop the Roma tomatoes and add them to the pot. Stir in the taco seasoning, allowing the flavors to meld together. Cook for an additional 2-3 minutes until the tomatoes start to break down.
Add the long-grain brown rice (or white) to the pot, stirring to combine with the vegetable mixture. Pour in the tomato sauce and 2 cups of water. Bring the mixture to a gentle boil.
Once boiling, reduce the heat to low, cover the pot, and let it simmer for 40-45 minutes (or about 20-25 minutes for white rice). Stir occasionally to prevent sticking, and check for doneness.
Once the rice is cooked and fluffy, stir in the drained black beans and cooked sweet corn. Mix well and allow everything to heat through for about 5 minutes.
Remove the pot from heat and stir in the nutritional yeast for a cheesy flavor. Adjust seasoning as needed with salt and pepper.
Scoop the Fiesta Rice and Black Beans into bowls and top with your choice of avocado, cilantro, chipotle crema, fresh tomatoes, hot sauce, dairy-free cheese shreds, tortilla strips, and a squeeze of lime juice for an extra zing.
