Choose the beans. Check that they do not have pebbles or other impurities. Rinse them in a strainer with plenty of running water.
Add the beans with the water and the onion cut into two halves in a pot, and cook over medium-high heat until it boils.
Once it comes to a boil, lower the heat to medium and cook, covered, for an hour or until the beans become soft. With a slotted spoon, remove and discard the foam that forms during cooking.
Meanwhile, in a large skillet over medium heat, fry the bacon in its fat for about 5 minutes until it begins to brown.
Add the onion and garlic and sauté until wilted, about 5 minutes.
Add the red bell pepper and the ají dulce, and sauté for 5 more minutes.
Add the sofrito, the papelón, and the spices: bay leaf, cumin, oregano, and black pepper to the pot with the beans. Season with salt, stir, and cook over medium heat, covered, for 30-45 minutes.
If the soup becomes too thick, add a couple of additional cups of water. If, on the other hand, you want it thicker, put a cup of soup (beans and liquid) in the vase of a blender, blend until a creamy, uniform mixture is formed, and add it back to the pot.
Adjust the salt and add a tablespoon of olive oil.
Serve with avocado and cilantro.