01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or grease lightly.
02 - In a large bowl, whisk together flour, sugar, poppy seeds, baking powder, baking soda, and salt until well blended.
03 - In a separate bowl, whisk eggs, milk, melted butter, lemon juice, lemon zest, and vanilla until smooth and fully incorporated.
04 - Pour wet ingredients into dry ingredients. Stir gently until just combined—do not overmix; a few small lumps are acceptable.
05 - Divide batter evenly among prepared muffin cups, filling each about 3/4 full.
06 - Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
07 - Allow muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.