Pat ribs dry with paper towels. Combine paprika, 1 tbsp of the onion powder, the salt and pepper in a small bowl. Rub onto both sides of ribs. Place meaty side up on a baking sheet fitted with a wire rack. Cover tightly with aluminum foil and refrigerate overnight.
Heat oven to 300° F. Transfer foil-wrapped ribs directly to oven and bake at 300° for 3 to 3 1/2 hours or until fork-tender.
Meanwhile, melt butter in a small pot over medium-low heat. Add garlic and cook 2 minutes or until softened. Stir in ketchup, honey, molasses, Worcestershire, vinegar, mustard and remaining 1 tsp onion powder. Simmer 15 minutes until sauce thickens. Cover and set aside (see Note).
Remove ribs from oven. Increase temperature to 400° F. Remove foil and brush ribs with 1 cup of the sauce. Return to oven, uncovered, and bake at 400° for 10 to 15 minutes until sauce is bubbly.
Slice ribs and serve with remaining sauce alongside.
Sauce can be made a day ahead and refrigerated. Yield is approximately 1 2/3 cups.
