Grilled Spare Ribs with Barbecue Sauce

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.