01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or grease lightly with cooking spray.
02 - In a large mixing bowl, whisk together flour, sugar, poppy seeds, baking powder, baking soda, and salt until evenly distributed.
03 - In a separate medium bowl, whisk eggs, milk, melted butter, lemon juice, lemon zest, and vanilla extract until fully incorporated and smooth.
04 - Pour wet ingredients into dry ingredients. Stir gently with a spatula or wooden spoon until just combined—some small lumps should remain. Do not overmix.
05 - Divide batter evenly among prepared muffin cups, filling each about three-quarters full.
06 - Bake for 18 to 20 minutes until golden brown and a toothpick inserted into the center of a muffin comes out clean.
07 - Let muffins cool in the tin for 5 minutes before transferring to a wire rack to cool completely.