In a large baking dish, combine rice, onion, bell peppers, garlic, spices and sea salt. Using a wooden spoon, stir everything together to ensure it is well combined.
Add in strained and rinsed black beans, evenly spreading them out in the dish.
In a separate bowl or container, whisk together vegetable broth (or water) and tomato paste until well combined. Pour over rice mixture and give it a good stir.
Cover baking dish with aluminium foil and transfer to the oven to bake for 30 minutes.
After 30 minutes, remove from the oven and give it a good stir. The mixture will still be a little soupy at this point, that is fine.
Return to the oven for an additional 25-30 minutes until rice is cooked and all of the liquid has been absorbed.
Uncover and fluff rice with a fork before serving.
Top with fresh cilantro, lime wedges and/or avocado.