Step 1: In a large Dutch oven or heavy-bottomed pot, cook the diced bacon over medium heat until crispy. Remove the bacon with a slotted spoon, reserving about 2 tablespoons of bacon grease in the pot. Crumble the cooked bacon and set aside.
Step 2: Add the diced onion and bell pepper to the reserved bacon grease. Sauté over medium heat for 5-7 minutes until softened. Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.
Step 3: Stir in the smoked paprika, chili powder, and dry mustard. Cook for 1 minute, stirring constantly, to toast the spices and release their aromas.
Step 4: Drain and rinse the canned kidney beans, pinto beans, and butter beans thoroughly. Add them to the pot, stirring to combine with the sautéed vegetables and spices.
Step 5: Pour in the crushed tomatoes, apple cider vinegar, molasses, brown sugar, and Worcestershire sauce. Stir everything together until well combined. Add the chicken or beef broth.
Step 6: Bring the mixture to a gentle simmer, then reduce the heat to low, cover, and let it cook for at least 45 minutes to 1 hour, or longer for deeper flavor. Stir occasionally to prevent sticking.
Step 7: Taste the cowboy beans and adjust seasoning as needed with salt, pepper, or additional brown sugar/vinegar for balance.
Step 8: Just before serving, stir in the crumbled, crispy bacon. Serve hot.