Line 15x10x1-inch baking pan with foil; spray foil with nonstick cooking spray. Place rack of ribs in single layer in sprayed foil-lined pan.
In small bowl, combine chili powder, celery salt and mustard; mix well. Sprinkle one side of ribs with half of spice mixture; turn and sprinkle other side with remaining spice mixture. Let stand at room temperature for 15 to 30 minutes.
Heat oven to 300°F. Bake ribs at 300°F. for 1 hour. Meanwhile, in small saucepan, combine all glaze ingredients; mix well. Bring to a boil over medium heat, stirring occasionally.
Remove ribs from oven; cool about 10 minutes. Increase oven temperature to 350°F. Cut ribs into individual riblets; return to baking pan in single layer. Brush one side of riblets with glaze.
Return to oven; bake at 350°F. for 15 minutes. Turn riblets; brush other side with glaze. Bake an additional 15 minutes. Discard any remaining glaze. Serve warm.