Buttermilk Blueberry Breakfast Cake

INGREDIENTS

½ cup unsalted butter, room temperature
2 tsp lemon zest or more (zest from 1 large lemon)
7/8 cup* + 1 tablespoon sugar**
1 egg, room temperature
1 tsp vanilla
2 cups flour
2 tsp baking powder
1 tsp kosher salt
2 cups fresh blueberries
½ cup buttermilk

* 7/8 cup = 3/4 cup + 2 tablespoons
** This 1 tablespoon is for sprinkling on top

Preheat the oven to 350ºF. Cream butter with lemon zest and 7/8 cup of the sugar until light and fluffy. Add the egg and vanilla and beat until combined. Meanwhile, toss the blueberries with ¼ cup of flour and set aside. In another bowl whisk together the remaining flour, baking powder and salt. Add the flour mixture to the batter a little at a time, alternating with the buttermilk. Fold in the blueberries. Grease a 9-inch square baking pan with butter or coat with non-stick spray. Spread batter into pan. Sprinkle batter with remaining tablespoon of sugar. Bake for 35 minutes. Check with a toothpick for doneness. If necessary, return pan to oven for a couple of more minutes. (Note: Baking for as long as 10 minutes more might be necessary.) Let cool at least 15 minutes before serving.