Blueberry Buttermilk Breakfast Cake

1. Preheat the oven to 350ºF.
2. Add sugar and lemon zest to a mixing bowl or bowl of a stand mixer fitted with the paddle attachment and rub together with your fingers until the sugar is moist and fragrant. Add the butter and beat until light and creamy.
2. 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.
3. Add the flour mixture to the batter a little at a time, alternating with the buttermilk. Fold in the blueberries.
4. 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 coarse sugar. Bake for 35-45 minutes, until an inserted toothpick comes out clean. Let cool a few minutes before serving.