Non-stick cooking spray
1 (20.0 oz.) box Martha White Blueberry Flavored Muffin Mix
1/3 cup butter, melted and divided
1/4 cup milk
1 large egg
2 teaspoons grated lemon peel
Heat Oven to 400°F. Coat 8-Inch Square Baking Pan with No-Stick Cooking Spray. Rinse and Drain Blueberries.
Place Muffin Mix in Large Mixing Bowl. Reserve 1 Cup Dry Mix for Topping. Combine 3 Tablespoons Melted Butter, Milk, Egg, and Lemon Peel. Stir into Muffin Mix Until Blended. Spread Evenly in Prepared Pan. Sprinkle Drained Blueberries Over Top. Combine Reserved Dry Mix and Remaining Melted Butter with a Fork Until Crumbly. Sprinkle Over Top of Batter.
Bake 17 to 20 Minutes or Until Toothpick Inserted in Center Comes Out Clean.
For Ease in Cutting, Line Entire Pan with Foil, Extending Foil Over Edge of Pan. Coat with No-Stick Cooking Spray. When Ready to Serve, Lift Coffee Cake Out of Pan Using Edges of Foil.