Preheat oven to 350 degrees F. Line a cupcake pan (12 cups) with paper liners. Set aside.

In a medium bowl, whisk the flour, baking powder, and salt together. Set aside. In a small bowl, combine the sugar and lemon zest. Rub together with your fingers until fragrant.

In a stand mixer, beat the butter and sugar mixture together until light and fluffy and lightened in color. This will take about 8 minutes. Scrape down the sides of the bowl with a rubber spatula.

Add the eggs one at at time, beating after each addition. Add in the vanilla.

Add the flour mixture and milk alternately, starting and ending with the flour. Mix until flour is just incorporated. Don't overmix. Mix in the lemon juice.

Divide batter evenly in prepared cupcake liners, filling 2/3 full. Bake cupcakes for 18-20 minutes or until a toothpick inserted in the center comes out clean. Transfer pan to a wire cooling rack and cool completely.

While the cupcakes are cooling, make the frosting. Using a stand mixer, beat the butter until creamy. With the mixer on low, add 1 cup of powdered sugar at a time until all of the powdered sugar is added. Beat in the milk, vanilla extract, and lemon zest. Beat until smooth.

To fill the cupcakes, using a knife, cut out a small hole in the center of the cupcake, about the size of a dime. Carefully remove the center piece and set aside. Fill each hole with about 1 teaspoon of lemon curd. Push the top of the cupcake piece you removed over the hole to cover up the lemon curd. A little lemon curd might squirt out and that is ok. Just wipe it off. You can leave the lemon curd showing if you wish and just eat the scraps. You will cover the hole with frosting. It works both ways.

Place the frosting in a pastry bag and frost. I used the 1M Wilton tip. Decorate with yellow sprinkles, if desired. Serve!

Note-Frosting can be made up to 2 days ahead of time and stored in the refrigerator. Let it come to room temperature and beat briefly before using. The lemon curd can be made up to two weeks in advance. Store in the refrigerator until ready to use. You can store the finished cupcakes in the refrigerator for 1-2 days. Let the cupcakes come to room temperature before serving. They are best the day they are made.