-
Preheat the oven to 350ºF. Cream butter with lemon zest and ⅞ 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 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. When the toothpick comes out clean from the middle of the cake, its done. . 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. This is important for settling. I'll warn you, its difficult waiting to dive into this cake.