Rinse the black beans in a colander and place in a medium saucepan. Add the onion, chile, and bay leaf and pour in enough water to cover the beans by 3 inches. Bring to a boil, then simmer over medium heat until the beans are very tender, 50 to 60 minutes. Season with the salt. Drain, reserving the cooking liquid.

For the rice, toast the cumin seeds in a small sauté pan over medium heat until they start releasing their assertive aroma. Let the seeds cool for a few minutes before you crush them to a powder in a mortar and pestle or spice grinder.

Heat the olive oil in a large saucepan over medium-high heat. Add the onion, red pepper, cilantro, and garlic. Cook the vegetables until soft, stirring constantly with a wooden spoon, 5 to 6 minutes. Stir in the ground cumin and salt. Add the rice and stir to mix the grains thoroughly with the sofrito. Add the water, bring to a boil, lower the heat, and simmer until the rice is tender, about 40 minutes. Cover with a lid and rest for 10 minutes.

Fluff the rice with a fork to separate the grains. Stir in the black beans with 1 cup (240 ml) of their cooking liquid and cook over medium-high heat until the liquid reduces in volume almost completely, 3 to 4 minutes. Taste for salt and adjust the seasoning as necessary. Let sit for a few minutes before serving. Store leftovers in the refrigerator. To reheat, sauté in a pan until warm all the way through.