Sweet BBQ Pit Sauce: In a saucepan, combine the dry ingredients and mix well to break up any lumps. Add ketchup, melted butter, water, vinegar, and Worcestershire sauce. Bring sauce to a simmer over low heat. Continue to simmer, stirring the entire time until the sauce has reduced and thickened, about 15 minutes. (Keeping the heat low helps prevent the butter from separating and the sugar from burning.)
Sauce is done when it thinly coats a spoon and has reduced by about ⅓. Cool to room temperature, stirring occasionally so it doesn’t stick to the bottom. Store in a covered container in the refrigerator. (It will keep for months, thanks to the vinegar.) Makes about 3 cups of Sweet BBQ Pit Sauce.
Prepare the vegetables and beef: Trim onion and pepper, then cut into chunks. Dice using a vegetable chopper, or use a knife to small dice (¼-inch pieces). Heat oil in a medium-sized skillet over medium heat. Sauté onion and pepper until softened, 6–8 minutes. Add ground beef, stir to break up meat, and continue cooking until meat is no longer pink, 6–8 minutes. Drain fat from skillet and set ground beef mixture aside.
Preheat oven to 375 F. In a large bowl, add ground beef mixture and Sweet BBQ Pit Sauce to the drained beans; stir to combine. Place in a 13x9-inch baking dish and cover with foil. Bake until brown and bubbly, 20–30 minutes. (Alternatively, a thermometer placed into the center of the beans should register 160 F.)
Remove dish from oven and remove foil. Stir and serve. Note: This is a great dish to make ahead of time. Vegetable-beef mixture can be cooked and refrigerated up to two days in advance. On the day of serving, simply mix bean ingredients (Pitmaster Jones calls this a “bean set”) and bake as directed. Since you're reheating meat, use a digital thermometer to make sure the beans reach 160-165 F for safe consumption.