Preheat oven to 375F.
Zest lemons into a bowl and set aside.
In a large bowl, whisk eggs and stir in sugar.
Add lemon zest, vegetable oil, vanilla and lemon juice, and stir until combined.
Then, mix in the sour cream.
Add flour, xanthan gum (if using), baking powder, and baking soda and stir together.
Spray the inside of a non-stick bundt pan with cooking spray and pour the batter into the pan.
Bake for 35 minutes.
Let cool in the pan for 10 minutes and then invert on a wire wrack to continue cooling. Sprinkle with powder sugar when cool and serve.