Pre-heat oven to 350 degrees. Using a stand or hand mixer, cream the butter with the lemon zest and 1 cup (minus one tablespoon) until light and fluffy.
Add the egg and vanilla until and beat until combined. While it is mixing, toss the berries with the 1/4 of flour you set aside. Then in a seperate bowl, wisk together the remaining flour, baking powder, and salt.
Add half of the flour mixture to your batter and fold in with a spatula. Add all of the buttermilk and stir. Add remaining flour and stir until all of the flour is absorbed into the batter. Fold in the blueberries with the spatula, leaving any extra flour from the berry bowl behind.
Grease an 8inX8in baking pan with butter or cooking spray. If you have parchment paper, line the pan on top of the butter. Spread the batter evenly into the pan and then sprinkle the remaining tablespoon of sugar previously set aside on the batter.
Place in the oven and bake for 40-45 minutes. Check for doneness with a toothpick. Your breakfast cake may need to cook longer so keep checking periodically with the toothpick. Decrease baking time if using a 9in pan down to 30-35 minutes.