Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a medium bowl, whisk together flour, baking soda, baking powder, salt, and poppy seeds.
In a separate large bowl, cream together butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each.
Mix in sour cream, lemon juice, lemon zest, and vanilla extract.
Gradually add dry ingredients to wet, mixing until just combined—do not overmix.
Divide batter evenly among the 12 liners.
Bake for 18–22 minutes or until a toothpick inserted comes out with a few moist crumbs.
Let cool in the pan for 5 minutes, then transfer to a cooling rack.
Frost with cream cheese frosting or drizzle with lemon glaze once fully cooled.