Preheat oven to 450 degree F. Line a 13 x 9 x 2-inch baking pan with foil. For rub, in a small bowl, combine cumin, coriander, chili powder, thyme, oregano, salt, and ground red pepper. Rub mixture onto both sides of ribs. Place ribs in prepared baking pan.
Bake, covered, in preheated oven for 1 hour. Carefully pour off fat and juices. Reduce oven temperature to 350 degree F. Sprinkle ribs with onion. In a medium bowl, combine salsa, vinegar, and garlic. Spoon sauce over ribs. Bake, covered, about 1 hour more or until tender.
To serve, transfer ribs to serving platter. Spoon sauce from pan over ribs. If desired, sprinkle with cilantro. Makes 6 servings.