01 - Preheat your waffle iron according to the manufacturer's instructions until indicator light shows ready temperature.
02 - In a large mixing bowl, whisk together all-purpose flour, granulated sugar, baking powder, baking soda, salt, and poppy seeds until evenly distributed.
03 - In a separate bowl, beat the eggs thoroughly. Whisk in milk, melted butter, fresh lemon juice, lemon zest, and vanilla extract until fully incorporated and smooth.
04 - Pour the wet mixture into the dry ingredients. Fold gently using a spatula or wooden spoon until just combined—stop when dry streaks disappear. Small lumps are acceptable; overmixing yields tough waffles.
05 - Lightly grease the preheated waffle iron with butter or nonstick spray. Pour appropriate amount of batter per manufacturer guidelines, close lid, and cook until golden brown and crisp (typically 4-6 minutes). Transfer cooked waffles to a wire rack or warm oven. Repeat with remaining batter.
06 - While waffles cook, combine fresh or frozen blueberries, granulated sugar, water, lemon juice, and lemon zest in a small saucepan over medium heat. Bring to a gentle simmer, stirring occasionally to dissolve sugar.
07 - For thicker consistency, dissolve cornstarch in 1 tablespoon cold water, then stir into the simmering berry mixture. Continue cooking for 2 additional minutes until syrup coats the back of a spoon. Remove from heat.
08 - Place hot waffles on serving plates. Ladle warm blueberry syrup generously over the top. Serve immediately while syrup is hot and waffles remain crisp.