01 - Preheat waffle iron according to the manufacturer's guidelines.
02 - Whisk together flour, sugar, baking powder, baking soda, and salt in a large bowl.
03 - In a separate bowl, whisk ricotta, milk, eggs, melted butter, lemon zest, lemon juice, and vanilla extract until smooth.
04 - Pour wet mixture into dry ingredients, stirring gently until just combined. Avoid overmixing for optimal texture.
05 - Fold in chopped toasted hazelnuts to distribute evenly.
06 - Lightly grease hot waffle iron with butter or oil.
07 - Ladle approximately 1/2 cup batter per waffle onto iron, spread evenly, close the lid, and cook 4 to 5 minutes until waffles are golden brown and crisp.
08 - Arrange waffles warm, topped with extra hazelnuts, optional powdered sugar, fresh berries, or a drizzle of honey.