Preheat oven to 350℉. Sift the gluten free flour, baking powder, and salt. Set aside. Whisk the sugar, egg, oil, lemon juice, lemon zest, and vanilla extract together. Add the dry ingredients and stir until smooth.
Pour the batter into a greased or lined muffin pan and bake for 15-20 minutes, or until a toothpick comes out clean. Let the muffins cool for at least 5 minutes before serving.