Heat the olive oil in a large, ovenproof pot over medium heat.
Add the chopped onion, bell pepper, and minced garlic.
Cook, stirring occasionally, until the onion is soft, about 5 minutes.
Add the washed black beans to the pot and cover with water.
Bring to a boil, then reduce the heat to a gentle simmer.
Cover loosely and cook until the beans are about half-done—softening but still firm in the center—about 40 minutes if soaked, or an hour or more if unsoaked.
Add more water as needed to keep the beans submerged.
While the beans cook, preheat your oven to 350°F / 175°C.
Once the beans are half-cooked, use an immersion blender or a potato masher to roughly puree them directly in the pot. Aim to leave at least half of the beans whole to maintain a nice texture.
Stir in the rice, chopped tomato, and a generous amount of salt and pepper. For a crispier crust, leave the pot uncovered.
Transfer the pot to the preheated oven and bake until the rice and beans are tender, about 30 to 60 minutes.
Check periodically and add a splash of water if the mixture looks too dry.
Once cooked, remove from the oven.
Taste and adjust seasoning with more salt and pepper if needed.
Sprinkle generously with fresh parsley or cilantro and serve immediately.
Don't over-puree the beans; leaving at least half of them whole provides essential texture and bite to the finished dish.