01 - Preheat the oven to 350°F. Line a 12-cup muffin pan with paper liners.
02 - In a medium bowl, whisk together flour, poppy seeds, baking powder, baking soda, and salt. Set aside.
03 - In a large bowl, cream butter and sugar together until light and fluffy, about 2 minutes.
04 - Add eggs, one at a time, beating well after each addition. Mix in lemon juice, lemon zest, and vanilla extract.
05 - Add the dry ingredients to the wet ingredients in three additions, alternating with the milk, beginning and ending with dry ingredients. Mix until just combined—do not overmix.
06 - Divide batter evenly among the cupcake liners, filling each about 2/3 full.
07 - Bake for 16–18 minutes, or until a toothpick inserted in the center comes out clean.
08 - Cool cupcakes in the pan for 5 minutes, then transfer to a wire rack to cool completely.
09 - Beat butter and cream cheese together until smooth. Gradually add powdered sugar, beating well. Mix in lemon juice, lemon zest, and salt.
10 - Once cupcakes are cool, frost generously with lemon cream cheese frosting. Garnish with extra lemon zest or poppy seeds if desired.