In a nonreactive pan over medium heat place the lemon juice and zest, just to warm not boil.
In a nonreactive bowl mix together the eggs, egg yolks, and sugar. Whisking until fully combined.
Slowly pour a small amount of the warmed lemon mixture into the egg mixture whisking until combined and add remained of the warm lemon mixture (this ensures the eggs are tempered, not scrambled!).
Once all of the lemon and egg mixture are fully combined add it all back to the pan and place over medium heat, stir continuously with a wooden spoon.
Cook for 2-3 minutes the temperature should be around 170F and when you draw a line with a spoon a line that quickly covers itself up should form.
You will notice the mixture has thickened up but still smooth.
Take off heat and immediately stir in butter cubes to bring the temperature down.
Once butter is fully combined add heavy cream, vanilla extract, and salt.
Pour into a container and cover with plastic wrap that is directly on to of the lemon curd.
You want it fully covered so a skin does not form on top.
Chill for at least 2 hours.
Use within 3 days.
