Preheat the oven to 350 degrees. Using a microplane zest a fresh orange.
Cream butter with orange zest and sugar until light and fluffy.
Add the egg and vanilla and beat until combined.
Toss the blueberries with ¼ cup of flour.
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" square baking pan (or something similar) with a non-stick spray. Spread batter into pan. Sprinkle batter with remaining tablespoon of sugar. Bake for 35 minutes. Check with a toothpick for doneness. If necessary, return pan to oven for a couple of more minutes. Bake for as long as 10 minutes more if necessary. Let cool at least 15 minutes before serving.
Notes
** Original recipe calls for lemon zest, but I have found the orange zest to be an exceptional combination with blueberries.
Recipe by Pray Cook Blog at https://praycookblog.com/blueberry-cream-coffee-cake-mornings-perfect-start/