A simple, summery, moist, blueberry breakfast cake with the perfect sweetness.
Preheat the oven to 350 degrees. Using a stand mixer or hand-held mixer, cream the butter with the lemon zest and the 1 cup minus 1 tablespoon of sugar until light and fluffy.
Add the egg and vanilla and beat until combined. Meanwhile, toss the blueberries with 1/4 cup of flour, then whisk together the remaining flour, baking powder and salt.
Add half of the flour mixture to the batter, and stir with spatula to incorporate. Add all the buttermilk. Stir. Add remaining flour, and stir until flour is absorbed. Fold in the blueberries. (Leave excess flour from the blueberry bowl behind.)
Grease an 8 or 9 inch square baking pan. Spread the batter into the pan. The batter will be very thick. Just press it as carefully as you can and try not to squish the blueberries. Sprinkle the batter with the remaining tablespoon of sugar. Bake for 35 to 45 minutes. Check with toothpick for doneness. Let cool at least 15 minutes before serving.
What if I don't have buttermilk? Place 2 teaspoons of vinegar or lemon juice into a liquid measuring cup. Fill cup with milk until it reaches the 1 cup line. Let stand for five minutes. Use as directed.