Heat the oven to 350 degrees. Coat 18 mini Bundt or fluted muffin cups with nonstick cooking spray with flour.
Combine the cake mix, 1 cup sour cream, oil and eggs in a large bowl and beat at medium speed for 2 minutes or until blended. Stir in 1 cup of the blueberries. Spoon into the muffin cups filling about 2/3 full.
Bake for 20 to 25 minutes or until lightly browned and a toothpick inserted in the center of cake comes out clean. Cool in the pans on a wire rack for 8 minutes. Gently loosen the edges with a small metal spatula and invert onto a wire rack. Cool completely.
Beat butter, lemon peel and remaining 1/4 cup sour cream in a medium bowl for 1 minute or until blended. Slowly beat in 3/4 cup powdered sugar, adding additional powdered sugar to desired consistency. Drizzle over the mini cakes and let stand until set.
Serve garnished with the remaining 1/2 cup blueberries.