Wrapped in foil, the spiced ribs oven-cook in intense heat; the foil locks in their moisture for supremely tender results. On with the sauce and over to the grill, and they're ready.
Preheat oven to 400 degrees. Season ribs with chili powder, salt, and pepper. Stack slabs on a double layer of aluminum foil; wrap tightly. Place on a rimmed baking sheet. Cook until meat is fork-tender, 1 1/2 to 2 hours.
Meanwhile, make barbecue sauce: In a medium saucepan, melt butter over medium heat. Add onion and garlic; season with salt and pepper. Cook until soft, 2 to 3 minutes. Add ketchup, vinegar, Worcestershire, cayenne, and desired variation (see below). Bring to a simmer. Cook, stirring occasionally, until slightly thick, about 5 minutes. Set aside.
Heat grill to medium-high; lightly oil grates. Carefully remove ribs from foil, pouring off any accumulated liquid. Brush ribs generously with sauce; grill until charred, 2 to 3 minutes per side. Serve with extra sauce, if desired.
The base of our 3 sauces is made with ketchup, vinegar, onion, garlic, and cayenne. Add one of the variations for a sweet, spicy, or smoky sauce.
Kansas City StyleIn step 2, stir in 1/2 cup packed light-brown sugar, 2 tablespoons molasses, and 1 tablespoon yellow mustard.Memphis StyleIn step 2, stir in 1/2 teaspoon hot sauce (such as Tabasco) and 1/4 cup sugar.Dallas StyleIn step 2, stir in 1 tablespoon chopped chipotle in adobo sauce and 1/2 teaspoon ground cumin.