Place pinto beans in a large bowl and cover with water by at least 2 inches. Let soak overnight (or at least 8 hours). Alternatively, for a quick-soak method, bring beans and water to a boil in a large pot, boil for 2 minutes, then remove from heat and let sit, covered, for 1 hour.

In a large Dutch oven or heavy-bottomed pot, cook the diced bacon over medium heat until it begins to crisp, about 5-7 minutes. Add the chopped onion and sauté until translucent, about 4-5 minutes. Add the minced garlic and cook for another 30 seconds until fragrant.

Drain and rinse the soaked beans, then add them to the pot. Pour in the 8 cups of fresh water and add the diced tomatoes with green chiles, chili powder, cumin, dried oregano, and bay leaves. Stir to combine.

Bring the mixture to a boil, then reduce heat to low, cover, and simmer for 2-3 hours, or until the beans are tender. Stir occasionally and add more water if needed to keep the beans submerged.

When beans are tender, add salt and black pepper. For those who enjoy a bit of heat, add the optional cayenne pepper. Continue to simmer uncovered for an additional 30 minutes to allow the flavors to meld and the liquid to thicken slightly.

Remove bay leaves before serving. Ladle the beans into bowls and garnish with fresh chopped cilantro. Serve with lime wedges on the side for a bright, acidic finish.