Preheat waffle maker. In a large bowl, combine flour, cornstarch, baking powder, baking soda and sugar.
In another bowl, whisk together lemon zest, lemon juice, butter, eggs, ricotta, vanilla extract and whole milk. Make a well in the dry ingredients and pour in the wet ingredients. Fold together the ingredients gently.
Spray the waffle maker with nonstick cooking spray. Portion the waffle batter into the waffle maker and close. Cook according to manufacturers instructions, until golden and crisp.