Pre-heat oven to 350°F.
Grease or line a standard loaf pan and set aside.
In a medium bowl combine 1 1/4 cups of gluten-free flour, baking powder, and salt. Set aside.
Add sugar and lemon zest to a small bowl, with clean hands rub the lemon zest into the sugar until well blended. Set aside.
In a small bowl add the blueberries with 1 tsp of gluten-free flour. Mix until blueberries are lightly coated with the flour.
In a large mixing bowl, beat softened butter for 2 minutes.
Add the lemon/sugar mixture to the butter and beat until light and fluffy an additional 1-2 minutes. Scrape down the sides of the bowl as needed.
Add in the vanilla extract.
Add each egg one at a time beating until each is fully mixed in.
Add in the flour mixture. Mix until fully combined.
Stir in the blueberries using a spatula or wooden spoon.
Pour the batter into the standard loaf pan.
Sprinkle the raw or turbinado sugar evenly over the top of the batter.
Bake for 40- 45 minutes or until a tester inserted into the center of the loaf comes out clean.
Let cake rest in pan for 5 minutes then remove to a cooling rack to cool.
Cool completely before serving.