Line a 12-serving standard muffin tin with paper liners and set aside. Preheat oven to 375°F.
In a large bowl, whisk together egg replacer and water and let sit while preparing remaining ingredients.
In a medium bowl, combine flour, sugar, baking powder, and salt. Set aside.
Add the melted butter, milk, and vanilla extract to the egg replacer mixture and whisk thoroughly. Fold in the dry ingredients until moistened. Add blueberries and fold to incorporate, taking care not to overmix.
Evenly portion the batter into the prepared muffin tin. Bake until a toothpick inserted in the center comes out clean, about 20 - 25 minutes.