01 - Preheat oven to 375°F and line a 12-cup muffin tin with paper liners or grease it thoroughly.
02 - Whisk together flour, sugar, poppy seeds, baking powder, baking soda, and salt in a large bowl.
03 - In a separate bowl, beat eggs with milk, melted butter, lemon juice, lemon zest, and vanilla extract until smooth.
04 - Pour wet mixture into dry ingredients and gently fold with a spatula until just combined, avoiding overmixing.
05 - Spoon the batter evenly into muffin cups, filling each about three-quarters full.
06 - Bake for 18 to 20 minutes or until a toothpick inserted in the center comes out clean.
07 - Let muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.