01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners.
02 - Whisk together flour, sugar, poppy seeds, baking powder, baking soda, and salt in a large bowl.
03 - Whisk eggs, milk, melted butter, lemon juice, lemon zest, and vanilla extract in a separate bowl until fully combined.
04 - Pour wet ingredients into dry ingredients. Fold gently with a spatula until just moistened; do not overmix.
05 - Divide batter evenly among muffin cups, filling each about 3/4 full.
06 - Bake for 18 minutes, or until a toothpick inserted into the center comes out clean.
07 - Let muffins cool in the tin for 5 minutes, then transfer to a wire rack.
08 - Whisk powdered sugar with 2 tbsp lemon juice until smooth. Adjust consistency with additional juice if needed.
09 - Drizzle glaze over cooled muffins and allow to set for 10 minutes before serving.