Step 1 In a heavy-bottom 4-quart pot, combine the onion, garlic, lemon zest and bourbon. Bring the bourbon to a simmer over medium-high heat, then reduce the heat to maintain a simmer and continue to cook until the onion is translucent, about 10 minutes.
Step 2 Stir in the lemon juice, pepper, chile powder, mustard, onion powder, salt, tomato paste, ketchup, vinegar, pineapple juice, liquid smoke, Worcestershire sauce, brown sugar, molasses, Tabasco and bitters and continue to gently simmer for 30 minutes. Stir frequently, making sure to scrape the bottom of the pot to prevent burning.
Step 3Remove from heat and puree the sauce until fairly smooth, using an immersion blender or blending in stages in a stand blender. Place the sauce in a nonreactive container and set aside until it comes to room temperature, then cover and refrigerate until needed. Warm the sauce before using.