Preheat your oven to 350 degrees.  Grease a 8 or 9 inch pan and set aside.  In a medium sized mixing bowl, cream together the butter, lemon zest, and sugar.  Add the egg and vanilla and beat until combined.

In a separate mixing bowl, whisk together the 1 and 3/4 cup flour, salt and baking powder.  Toss the blueberries in the remaining 1/4 cup flour.

Add the flour mixture to the creamed mixture a little at a time alternating with the buttermilk until combined.  Gently fold in the blueberries.  

Spread the batter into the prepared baking pan.  Sprinkle with coarse sugar.  Bake for 35-40 minutes or until it is cooked through and toothpick is clean.  Let rest for 15 minutes before serving.