Use a dark beer with a lot of character for this recipe. Good candidates include Newcastle Brown Ale, Samuel Smith Oatmeal Stout, or Dragon Stout from Jamaica.
Step 1: Melt the butter in a saucepan over medium heat. Add the bacon and onion and cook until both are a deep golden brown, 5 to 8 minutes. If the onion starts to burn, reduce the heat.
Step 2: Add the beer and boil until reduced by half. Add the ketchup, Worcestershire sauce, brown sugar, mustard, lemon juice, hot sauce, liquid smoke, and 1/2 cup water. Let the sauce simmer until mellow, thick, and richly flavored, about 10 minutes, stirring often with a wooden spoon. Taste for seasoning, adding salt and pepper to taste; the sauce should be highly seasoned. Let the sauce cool to room temperature before serving. The sauce can be refrigerated, covered, for up to 1 week. Let return to room temperature before serving.