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 bowl, whisk eggs, milk, melted butter, lemon juice, lemon zest, and vanilla extract until smooth and well combined.
04 - Pour wet ingredients into dry ingredients. Fold gently with a spatula until just combined. The batter should remain slightly lumpy—avoid overmixing to prevent tough muffins.
05 - Divide batter evenly among prepared muffin cups, filling each about three-quarters full.
06 - Bake for 18–20 minutes, or until a toothpick inserted into the center of a muffin comes out clean and tops are golden brown.
07 - Let muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.