Preheat oven to 350º F and flippantly grease a 9×5-inch baking dish with butter or non-stick spray.
In a big bowl or mixer, cream collectively butter, sugar and lemon zest for 3-5 minutes, or till fluffy, and lightened in colour.
Beat in egg, then, as soon as totally included, add in vanilla extract.
In a separate bowl, whisk collectively remaining flour, baking powder, salt and cinnamon, if utilizing.
Alternating between the flour combination and the add each to the batter, starting and ending with the dry components.Alternating between the flour combination and the buttermilk, add each to the batter, starting and ending with the dry components.
Fold floured blueberries into the batter, then pour it into greased baking dish. Prime with 1 tablespoons sugar, then place dish in oven.
Bake for 40-50 minutes, or till toothpick inserted in middle comes out clear.
Take away from oven and switch to a wire rack to chill (not less than quarter-hour).