Preheat oven to 350 degrees.
2. Whisk together flour, sugar, baking soda and baking powder in a large mixing bowl.
3. Add butter, egg whites, vanilla, sour cream, milk, lemon juice and zest and mix on medium speed until smooth.
4. Gently fold the blueberries into the batter.
5. Fill cupcake liners a little more than half way.
6. Bake 18-20 minutes.
7. Allow to cool for 1-2 minutes, then remove to cooling rack to finish cooling.
8. While cupcakes cool, make icing. Beat butter and shortening together until smooth.
9. Add two cups of powdered sugar and mix until smooth.
10. Add lemon juice, lemon zest and vanilla and mix until smooth.
11. Add remaining powdered sugar and mix until smooth.
12. Ice cupcakes when cool.