Preheat oven to 375°F (190°C). Line a muffin tin with paper liners or grease lightly.

In a medium bowl, whisk together flour, poppy seeds, baking soda, and salt.

In a large bowl, beat butter and sugar until light and fluffy. Add eggs one at a time, then mix in sour cream, milk, lemon zest, lemon juice, and vanilla.

Gradually add dry ingredients to the wet mixture and stir just until combined.

Divide batter evenly among muffin cups.

Bake for 18–20 minutes, or until a toothpick inserted into the center comes out clean. Cool before serving.