1. Preheat the oven to 350ºF. Cream butter with lemon zest and the sugar (keep 1TBS separate) until light and fluffy.

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 remaining tablespoon of sugar. Bake for 35 to 45 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.