Preheat your oven to 350°F (175°C). Line a 12-cup muffin pan with cupcake liners.
In a bowl, whisk together the flour, poppy seeds, baking powder, baking soda, and salt.
In a separate large bowl, beat the butter and sugar together until light and fluffy.
Add eggs one at a time, beating well after each addition. Mix in the sour cream, lemon juice, lemon zest, and vanilla extract.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
Divide the batter evenly among the cupcake liners, filling each about two-thirds full.
Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Allow cupcakes to cool in the pan for 10 minutes then transfer to a wire rack to cool completely.