Preheat the oven to 350°F (175°C) and line a muffin tin with cupcake liners.

In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition.

Stir in the buttermilk, lemon zest, and lemon juice.

In another bowl, whisk together the flour, baking powder, baking soda, salt, and poppy seeds.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Divide the batter evenly among the cupcake liners, filling each about 2/3 full.

Bake in the preheated oven for 15-18 minutes, or until a toothpick inserted into the center comes out clean.

Remove from the oven and let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

In a mixing bowl, beat together the softened cream cheese and butter until smooth.

Gradually add the powdered sugar, mixing until well combined.

Stir in the lemon juice and vanilla extract until smooth and creamy.

Once the cupcakes are completely cool, frost them with the lemon cream cheese frosting using a spatula or piping bag.

Optional: Garnish with additional lemon zest or poppy seeds if desired.