½ cup unsalted butter, room temperature
2 tsp. lemon zest or more — zest from 1 large lemon
7/8 cup* + 1 tablespoon sugar**
1 egg, room temperature
1 tsp. vanilla
2 cups flour (set aside 1/4 cup of this to toss with the blueberries)
2 tsp. baking powder
1 tsp. kosher salt
2 cups fresh blueberries
½ cup buttermilk***