Preheat oven to 350°F and lightly grease a muffin tin.
In a mixing bowl, whisk together sugar and flour.
Add melted butter, eggs, milk, lemon juice, zest, and vanilla. Whisk until smooth.
Pour the batter evenly into the prepared muffin tin.
Bake for 25 to 30 minutes until golden and set in the center.
Cool before removing from the tin. The pies will create their own crust, filling, and top.