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, vanilla extract, lemon zest, and poppy seeds.

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

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

Spoon the batter into the prepared muffin tin, filling each liner about 2/3 full.

Bake in the preheated oven for 18-20 minutes or until a toothpick inserted into the center comes out clean.

Remove from the oven and let the cupcakes cool in the tin for 5 minutes before transferring to a wire rack to cool completely.

In a mixing bowl, beat the softened butter until creamy.

Gradually add the powdered sugar, mixing until smooth.

Add the lemon juice and lemon zest, mixing until well combined. Adjust consistency with milk if needed.

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

Optional: Garnish with additional lemon zest or poppy seeds.