Preheat the oven to 350°F. Line a 12-count cupcake pan with paper liners and set aside.

In a medium mixing bowl, whisk together the flour, baking powder, baking soda, salt, and poppy seeds. Set aside.

In a large mixing bowl with a hand mixer, beat the softened butter and sugar until light and fluffy, about 2-3 minutes.

Add the eggs, mix until combined.

Mix in the vanilla extract, lemon zest, sour cream, milk, and lemon juice.

While mixing on low speed, gradually add the dry ingredients until completely combined.

Add a few drops of yellow gel food coloring for a vibrant hue, if desired.

Divide the batter evenly between the 12 cupcake liners, filling each about ⅔ full.

Bake for 16-18 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cupcakes to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

In a small saucepan, whisk together the egg yolks, sugar, lemon juice, and zest.

Cook over medium-low heat, stirring constantly with a rubber spatula or wooden spoon, until the mixture thickens enough to coat the back of the spoon (about 5–7 minutes).

Remove from heat and stir in the butter until smooth.

Transfer to a small bowl and chill in the refrigerator for 30 minutes before using.

In a large mixing bowl, beat the softened cream cheese, vanilla extract, and butter until smooth and creamy.

Gradually add the powdered sugar, one cup at a time, mixing on low until fully combined.

Transfer to a piping bag with a large star tip.

Use a small paring knife or cupcake corer to cut a small hole in the center of each cooled cupcake.

Fill each cavity with about 1 tablespoon of lemon curd using a piping bag or spoon.

Pipe the cream cheese frosting over the filled cupcakes, covering the lemon curd.

Garnish each cupcake with a sprinkle of poppy seeds, a thin slice of lemon, or edible flowers for an elegant finish.