Preheat oven to 350-degrees F.

Shortbread Crust

• Using an electric mixer, cream softened butter, then mix in sugar until blended.
• Add lemon zest until combined.
• Finally, add flour, and mix until blended.
• Press shortbread dough into a 9" springform pan. Bake for 15 minutes, or until golden around the edges.

Cheesecake

• Meanwhile, clean mixing bowl, then add softened and cubed cream cheese. Mix until creamy.
• Add sugar, and zest, and mix to incorporate.
• Mix in one egg at a time, scraping down the sides of the bowl when necessary.
• Add limoncello and vanilla. Mix until well combined.
• When ready, remove shortbread crust from the oven. Pour the cheesecake filling into the pan. Gently tap on the counter a few times to settle the filling.
• Fill a pie tin with some water and place on the bottom shelf of the oven to create steam while the cheesecake cooks. This helps to keep the cheesecake from cracking.
• Place cheesecake on the middle rack and bake at 350-degrees F. for approximately one hour, or until the cake has fully risen, and there is no indent in the center of the cheesecake. Sometimes it's necessary to turn off the heat and leave the cheesecake in the oven so that the center is fully cooked.
• Remove cheesecake from the oven and leave on the counter (uncovered) until completely cool. 

Lemon Curd

• While the cheesecake is baking, add all lemon curd ingredients (except butter) into a small saucepan. Whisk over low heat until smooth.
• Add butter and continue to whisk over low to medium heat until the lemon curd thickens. Allow to cool.
• When the cake has cooled off, spread lemon curd over it and smooth it out.
• Chill in the refrigerator for approximately four hours or overnight before serving.