Preheat oven to 350 degrees and line 12 muffin cups with paper liners spray with baking spray.

In mixing bowl beat the butter and sugar until light and fluffy. Add the eggs, one at a time, beating well after each addition. Add in the vanilla extract and lemon zest.

In a medium bowl whisk together the flour, baking powder, and salt.

With the mixer on low speed, alternately add the flour mixture and milk, in three additions, beginning and ending with the flour. Scrape down the sides of the bowl as needed.

Fill the muffin cups with batter. Bake for about 19 - 20 minutes. Once the cupcakes have cooled completely, cut a deep hole in the center of each cupcake, using a melon baller or small pairing knife.

While cupcakes are baking

In a glass or stainless steel bowl place eggs, sugar and lemon juice and whisk to blend. Place bowl over simmering water. Cook, stirring constantly (to prevent it from curdling), until the mixture becomes thick like yogurt. This will take approximately 10 minutes.

Remove from heat and immediately pour through a fine strainer to remove any lumps. Cut the butter into small pieces and whisk into the mixture until the butter has melted. Add the lemon zest and let cool.

The lemon curd will continue to thicken as it cools. Cover immediately with plastic wrap. Place wrap directly on curd so a skin doesn't form and refrigerate until cold at least 30 minutes. The lemon curd can be made several days (up to a week) in advance.

After curd is completely cool take a spoon and fill each hole in cupcake.

In a large mixing bowl place the whipping cream, vanilla extract, and sugar and stir to combine. Beat the mixture until stiff peaks form. Spread or pipe frosting on each cupcake. You can store in refrigerator until ready to serve.