1. Weigh or lightly spoon pancake mix into dry measuring cups; level with a knife. Place pancake mix in a medium bowl. Combine egg, buttermilk, oil, and 1 tablespoon lemon rind, stirring with a whisk; add to pancake mix, stirring until smooth. Fold in 1/2 cup blueberries; let stand 5 minutes.
2. While batter stands, combine powdered sugar, butter, and remaining 1 tablespoon lemon rind, stirring with a fork.
3. Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Pour about 1/4 cup batter per pancake onto hot pan. Cook 1 minute or until tops are covered with bubbles and edges look cooked. Carefully turn pancakes over; cook 1 minute or until bottoms are lightly browned. Repeat procedure with remaining batter.
4. Spread pancakes evenly with butter mixture and top evenly with remaining 1 cup blueberries.