Preheat a waffle maker to medium heat.
In a medium bowl, mix together whole-wheat flour, all-purpose flour, baking powder, baking soda, and salt.
In another large mixing bowl, whisk together the eggs, lukewarm milk, lemon juice, vanilla, ricotta, and melted butter.
Add the flour mixture to the wet mixture, add the erythritol or stevia, and stir just until the batter is just combined.
Fold in the blueberries and lemon zest.
Once the waffle iron is heated, spray it with cooking spray if needed. Pour about 1/4 cup of the batter into each well of the waffle plate. Close the lid and cook until the waffles are golden brown and crisp.
Serve immediately with favorite toppings and enjoy!