Meanwhile, heat oil in a large skillet over medium-high heat.
Saute onions and green pepper in oil until softened and lightly browned around the edges.
Mix in garlic, cumin, oregano, and red pepper flakes; cook for about 30 seconds, stirring constantly, until fragrant.
Stir in black beans, then reduce heat and simmer for about 5-10 minutes or until liquid from the beans is reduced/forms a sauce and veggies are tender. Add a little water if the beans get too dry.
Serve beans over rice, sprinkled with cilantro if desired. Enjoy!