Double Blueberry Muffins

This recipe is from the July/August everyday Food Magazine. Delicious recipe, not overly sweet.
1/2 cup (1 stick) unsalted butter, room temperature
3/4 cup plus 1 tablespoon sugar
2 large eggs
2 cups fresh blueberries, rinsed and dried
1 tablespoon grated lemon zest, (from 1 lemon)
1 cup all-purpose flour (spooned and leveled)
1 cup yellow cornmeal
2 teaspoons baking powder
1/2 teaspoon salt
1/2 cup milk
Directions
Preheat oven to 375 degrees. Line a standard (12-cup) muffin tin (or two 6-cup tins) with paper cups. With an electric mixer, cream butter and 3/4 cup sugar on medium-high speed until fluffy. Add eggs, one at a time; beat until combined.
In a shallow bowl, mash 1/2 cup blueberries with a fork until liquefied. Add to butter mixture, along with lemon zest; beat to incorporate (mixture will appear separated).
In a large bowl, whisk together flour, cornmeal, baking powder, and salt. Gradually add flour mixture and milk to the butter mixture in alternating batches, beginning and ending with the flour. Gently fold in remaining 1 1/2 cups blueberries.
Spoon or scoop batter into cups, and sprinkle tops with remaining tablespoon sugar. Bake until a toothpick inserted in the center of a muffin comes out clean, about 25 minutes. Cool in pan 20 minutes, then turn out muffins onto a wire rack to cool 10 minutes more before serving.