I highly recommend using a scale to measure the gluten free flour for this recipe.
Preheat oven to 330oF (165oC). Line a standard 6 cups muffin pan with cupcake liners. Set aside.
To a bowl, add sugar and water. Whisk until sugar is completely dissolved.
Then add oil and mix well.
Sift in flour, baking powder and baking soda.Mix well for 1-2 minutes. This is give more structure to the batter. Cupcakes will not be rubbery since we are using gluten free flour. Then, add vanilla extract and lemon juice and mix well.
Spoon batter into cupcake liner until 2/3 full.
Bake in preheated oven to 330oF (165oC), rack middle position, 20-22 minutes, or until toothpick inserted in the middle of cake comes out clean.
Let cupcakes cool down in pan for 10 minutes. Then transfer cupcakes to wire rack to cool down completely.