Preheat the oven to 425F.
Line a 12-count muffin pan with paper liners & set aside.
In a small bowl, stir together flour, baking powder, baking soda, salt and poppy seeds, set aside.
Beat the butter on high speed until creamy, then add sugar & beat together.
Add the eggs, vanilla extract, lemon zest & sour cream, mix just until combined.
Fold in the lemon juice and then add the flour mixture & mix until just combined.
Spoon batter into prepared pan, filling each well 3/4 full.
Bake for 5 minutes at 425F degrees, then lower the oven temperature to 350F degrees & bake for 10-15 minutes more or until a toothpick test comes out clean.