Preheat oven to 375 degrees and fill cupcake tray with liners.
Combine all dry ingredients (flours, flax, chia, baking powder, baking soda, and salt) and set aside
Beat butter with sugar until light and fluffy, about 2 to 3 minutes
Add eggs one at a time until incorporated
Add buttermilk and vanilla and continue beating on low/medium speed
Add lemon zest if using and dry ingredients and beat only until combined
Gently fold in blueberries
Fill cupcake liners to the top
Bake for 25 minutes