Sticky Spicy Ribs

For ribs
2 tablespoons packed dark brown sugar
1½ teaspoons salt
2 tablespoons paprika (not hot)
1½ teaspoons chipotle chile powder
½ teaspoon black pepper
2 (2-lb) racks baby back ribs

For sauce
1½ cups chopped onion (from 1 large)
6 garlic cloves, finely chopped
1½ tablespoons finely chopped peeled fresh ginger
2 tablespoons vegetable oil
1½ cups ketchup
½ cup cider vinegar
6 tablespoons soy sauce
½ cup water
¼ cup packed dark brown sugar
1½ teaspoons salt
¾ teaspoon black pepper

Whisk together brown sugar, salt, and spices in a small bowl. Line a 17- by 12- by 1-inch heavy-duty baking pan with a double layer of foil, then oil foil. Pat ribs dry and arrange in baking pan. Rub ribs all over with spice mixture and marinate, meaty sides up, covered and chilled, 2½ hours. Bring ribs to room temperature, about 30 minutes. Put oven rack in middle position and preheat oven to 350°F. Cover pan tightly with foil; bake 1¼ hours. Remove foil.

Make sauce while ribs bake: Cook onion, garlic, and ginger in oil in a 2-quart heavy saucepan over moderate heat, stirring occasionally, until softened, about 6 minutes. Add remaining ingredients and simmer, uncovered, stirring occasionally, 15 minutes. Purée sauce in 2 or 3 batches in a blender until smooth (use caution when blending hot liquids). Set aside 1 cup sauce for serving with ribs.

To cook ribs using a gas grill: Lightly oil grill rack, then transfer ribs to rack above shut-off burner, reserving pan juices. Grill, covered with lid, basting generously with pan juices and sauce and turning over and rotating ribs every 10 minutes (keep ribs over shut-off burner), until ribs are tender and browned, 30 to 40 minutes total. Transfer ribs to a cutting board and let stand 5 minutes before cutting into individual ribs. (If you aren’t able to grill outdoors, after baking ribs covered, remove top sheet of foil and continue to bake ribs, uncovered, basting generously with sauce and pan juices every 10 minutes and turning ribs after 20 minutes, 40 minutes total. Then turn on broiler and broil ribs, meaty sides up, 4 to 6 inches from heat until browned, about 3 minutes.)