With an electric mixer (I use a Kitchen Aid mixer), beat egg whites for approximately 5 minutes or until quite frothy.
Add the sugar, vanilla, oil and lemon flavouring and continue to beat for 30 seconds until mixed together well.
In a separate bowl, combine the flour and baking powder. Add blueberries and stir until blueberries are coated.
Add the dry ingredients to the wet ingredients and gently fold together (with a spatula) until combined. Be sure not to over fold as the cake will turn out too dense.
Pour ½ cup of blueberries into the bottom of a bundt or tube pan. Pour batter into pan. Bake at 350 degrees F for 45 - 60 minutes or until toothpick inserted comes out clean.
Let cake COOL in the pan on a cooling rack.
For the glaze, in a small bowl or measuring cup, stir together icing sugar, maple syrup and 2 tsp milk.
Continue to add a small amount of milk until the icing runs off of your fork.
Turn cake out of pan onto a plate and drizzle the glaze over top.
You can use lemon juice instead of lemon flavouring.
You can use fresh blueberries instead of frozen.