Beat eggs and sugar with a mixer. They add the milk and the oil and beat again. In a separate bowl pour the flour and baking powder, add to it. Then add it to other products and stir until a thick mixture (if necessary, add more flour). Finally grate lemon peel, add to the mix, as well as vanilla (you and liquid) and stir with a spoon. Remove the appropriate tray and rub in the butter. Pour the mixture into it and bake in a moderate oven.