Lemon Curd

1. In a medium heavy bottom saucepan, add the sugar and eggs. Whisk ingredients to combine. 
2. Pour lemon juice into sugar-egg mixture and whisk to combine. 
3. Under medium heat, cook curd while whisking consistently. Curd is ready once it has thickened up and coats the back of spoon/spatula, about 10-12 minutes. The temperature of curd should register 165-170F on a kitchen thermometer.
4. Remove curd from heat.
5. Pass hot curd through a fine mesh sieve/strainer into a bowl and discard any remnants of cooked eggs, if present.
6. Slowly whisk butter into warm curd a little at time (about 1 tablespoon) until completely incorporated. 
7. Whisk the lemon zest into curd, if using before, covering the surface of curd with plastic/cling wrap.
8. Refridgerate lemon curd for at least 2-4 hours or overnight. Curd will continue to thicken up as it cools.

Lemon Cupcakes

1. Preheat oven to 350F(177C). Line a 12-count cupcake baking pan with cupcake liners. 
2. In a medium mixing bowl, add flour, baking powder and salt. Whisk ingredients to combine.
3. In a separate medium mixing bowl, add the sugar and lemon zest. Use fingertips to rub zest into sugar until it is fully mixed in and sugar-zest mixture becomes aromatic, about (1) minute.
4. In the bowl of a stand mixer fitted with paddle attachment or in a large mixing bowl and hand-held mixer, add the lemon sugar, butter and oil.
5. Mix ingredients together at medium high speed until light and fluffy in appearance, about 2-3 minutes.
6. Next, beat eggs into butter mixture one at a time ensuring each egg is properly mixed into batter before adding the next egg. 
7. Reduce mixer speed to low. Mix in half of the flour mixture into wet batter, followed by the milk, lemon juice and vanilla extract and ending with the remaining flour mixture.
8. Stop mixer and use a spatula to scrape the sides and bottom of mixing bowl. Turn mixer back on to low speed and mix cupcake batter for an additional minute.
9. Evenly divide cupcake batter into prepared cupcake pan and bake for 18-20 minutes, rotating the pan halfway through bake time. Cupcakes are ready when a toothpick inserted into the center of one of them comes out clean.
10. Allow cupcakes to rest in pans for 5 minutes before transferring to a cooling rack to completely cool to room temperature.

Lemon Cream Cheese Frosting

1. In the bowl of a stand mixer fitted with paddle attachment or in a large mixing bowl and a hand-held mixer, add the cream cheese, butter, and lemon zest. 
2. Beat cream cheese mixture together at medium high speed until mixture is smooth and lump free, about 1-2 minutes.
3. Reduce mixer speed to low and slowly mix in the confectioner’s sugar 1 cup at a time. 
4. Once all of the powdered suger has been mixed into frosting, stop mixer. Use a spatula to scrape the sides and base of mixing bowl.
5. Resume mixing frosting for an additional minute at medium speed until smooth in appearance.  
6. If lemon cream cheese frosting appears too soft to pipe, refrigerate frosting for 30-60 minutes. This will allow frosting to reach a firmer consistency to pipe. (I prefer this method over mixing in additional sugar which can result in an overly sweet frosting). See notes below on how to siften up soft frosting without refrigeration. 

Assembly

1. Core about 1/2 inch out the center of cooled cupcakes. I used this tool to remove the center portion out of cupcakes but this cupcake corer is great as well. 
2. Spoon 1/2 cup of the lemon curd into a standard pastry bag and snip 1/4 inch off the tip of the bag.
3. Pipe enough of the lemon curd into the center of each cupcake just until the surface is reached. Refill pastry bag with lemon curd as needed.
4. Spoon the lemon cream cheese frosting into a separate pastry bag fitted with a 1M Wilton pastry tip. Starting in the center of each cupcake, pipe frosting in a circular motion until the outer rim is reached.
5. Next, pipe a border on top of base frosting layer.
6. Fill the center of each piped border with remaining lemon curd.