Lemon Custard

Wash and dry the lemons. Using a fine grater or a zester, zest the lemons to create 1 tablespoon of zest.
Cut the lemons in half and juice them to make ¼ cup of juice.
Place sugar, cornstarch, and lemon zest in a medium saucepan, whisk to combine.
Whisk in egg yolks, milk, and cream.
Heat over medium-low heat while whisking until thickened and the mixture starts to boil. This will take about 15 minutes.
Once boiling, let bubble for 1 minute while whisking. Remove from the heat and stir in butter, lemon juice, and vanilla.
Pour into a medium bowl.
Immediately cover with plastic wrap, resting the wrap on the surface of the custard.
Refrigerate at least 2 hours.