Heat oven to 375°F. Grease and flour 8-inch square baking pan; set aside.
Combine all cake ingredients except blueberries in bowl. Beat at low speed, scraping bowl often, until well mixed. Gently fold in blueberries. Spread batter into prepared pan.
Stir together all topping ingredients except butter in bowl; cut in butter until mixture resembles coarse crumbs. Sprinkle mixture over batter. Bake 40-45 minutes or until toothpick inserted in center comes out clean.
Recipe courtesy of Bettina Tolin, Executive Chef at Marcello’s Italian Restaurant in Port Isabel.