Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners, spray the liners with cooking spray.
First, make your vegan buttermilk by mixing together the non-dairy milk and lemon juice. Let sit for 5 minutes.
In a small bowl, mix together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, cream together the butter and sugar (for about 5 minutes). Then add the vegan egg and vanilla extract and mix until combined.
Add the dry ingredients and buttermilk and mix with a wooden spoon or spatula until just combined, do not overmix. Fold in the blueberries.
Scoop the batter into the prepared muffin tin. Sprinkle each muffin with turbinado sugar. Bake for 25-30 minutes, until toothpick inserted into the center of a muffin comes out clean. Let the muffins sit in the pan for about 5 minutes before transferring them to a wire rack to finish cooling.