I swear buttermilk is magic. I’ve dwelled on this before. Buttermilk seems to turn everything to gold. Super-moist, super-delicious gold.
½ cup unsalted butter, room temperature
2 tsp. lemon zest or more — zest from 1 large lemon
⅞ cup* + 1 tablespoon sugar for sprinkling
1 egg, room temperature
1 tsp. vanilla
2 cups flour (set aside ¼ cup of this to toss with the blueberries)
2 tsp. baking powder
1 tsp. kosher salt
2 cups fresh blueberries
½ cup buttermilk*** ⅞ cup = ¾ cup + 2 tablespoons** To make homemade buttermilk, place 1 tablespoon of vinegar or lemon juice in a liquid measuring cup. Fill the cup with milk until it reaches the 1-cup line. Let stand for five minutes. Use the only ½ cup of the prepared mixture for the recipe.
1- Preheat the oven to 350ºF. Cream butter with lemon zest and a ⅞ cup of the sugar 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 the 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.