Preheat the oven to 350°F (175°C) and line a muffin tin with paper liners.
In a large bowl, cream together the butter and sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the lemon zest and juice.
In another bowl, sift together the flour, baking powder, baking soda, and salt. Gradually add to the creamed mixture with the poppy seeds and sour cream, mixing until just combined.
Spoon the batter into the prepared muffin cups, filling each about two-thirds full.
Bake in the preheated oven for 18-20 minutes or until a toothpick inserted into the center of a muffin comes out clean.
Allow muffins to cool in the pan for a few minutes before transferring to a wire rack to cool completely.
Notes
These muffins can be stored in an airtight container for up to 3 days. For a longer shelf life, refrigerate them.