Step 1

Bring beans, bay leaf, ¼ cup chopped onion, ¼ cup chopped bell pepper, 1 Tbsp. grated garlic, 5 tsp. Diamond Crystal or 1 Tbsp. Morton salt, ½ tsp. oregano, and 5 quarts water to a boil in a large pot. Reduce heat to medium and cook, stirring occasionally and adding more hot water if needed to cover, until beans are tender and covered by about ¼" liquid, 2½–3 hours. Discard bay leaf.

Step 2

Meanwhile, heat oil in a medium skillet over medium-low. Add remaining onion, bell pepper, garlic, and oregano; season with salt and pepper. Cook, stirring occasionally, until onions are very soft and beginning to brown, 15–20 minutes. Stir into cooked beans. Top with cilantro, if using.

Step 3

Do Ahead: Beans can be made 3 months ahead. Transfer to an airtight container and freeze.