Steps
1. Heat olive oil in a skillet over medium heat.
2. Add sliced onions and sauté for 2-3 minutes until translucent.
3. Stir in the bell pepper and jalapeño (if using), cooking for another 2-3 minutes until softened.
4. Add the black beans, cumin, salt, and pepper. Stir well to combine and heat through for about 5 minutes.
5. Serve hot, garnished with fresh cilantro and a squeeze of lime if desired.