Preheat oven to 425°F. Line a muffin tin with baking cups, or spray tin liberally with cooking spray. Set aside.
In a medium-size mixing bowl, combine the plant-based milk, lemon juice, and lemon zest. Let rest for about 5 minutes to allow the mixture to curdle.
When the mixture has curdled, add in the oil or melted butter, maple syrup, and vanilla. Whisk to combine.
Next, add in the flour, baking powder, baking soda, and salt. Stir until well incorporated, but do not over-mix (this makes for tough muffins)—a few lumps of flour are fine. Add in the blueberries, and fold to combine.
Fill each muffin cup about ¾ full with the batter, and then sprinkle tops with sugar. Bake in the preheated oven for 12-15 minutes, or until a toothpick inserted into the center of a muffin comes out cleanly. Remove from the oven, and allow to cool for five minutes in the pan, and then transfer to a cooling rack to cool completely.