Blueberry Breakfast Cake

This breakfast cake was wonderful and we actually ate it for dessert this week instead of for breakfast.  Everyone in my family really liked it and it was so light and fluffy.

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 (set aside 1/4 cup of this to toss with the blueberries)
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
*** To make homemade buttermilk, place 1 tablespoon of vinegar or lemon juice in a liquid measuring cup. Fill cup with milk until it reaches the 1-cup line. Let stand for five minutes.

DIRECTIONS
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, then 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 (or something similar) 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.