In a medium saucier pan (rounded bottom rather than square, which is a sauce pan), combine the sugar and cornstarch.
Stir in lemon peel (I use a microplane grater, then mince the peel so its very small) and lemon juice.
Add butter.
Cook over medium-high heat, stirring, until thick and bubbly.
Carefully whisk half the lemon mixture into the beaten eggs, making sure that it mixes immediately so the hot mixture doesn't cook the eggs.
When incorporated, whisk the egg mixture into the pan with the rest of the lemon mixture.
Cook and stir for about two minutes more. Pour into sterilized canning jars, or into a serving bowl if using that day, and cover with waxed paper and cool. Makes about one cup of lemon curd.
I give my jars of curd a turn in simmering water for about 5 minutes, just to make sure that it keeps, and I store it in the refrigerator.
Recipe by Finch Frolic Garden Permaculture at https://www.vegetariat.com/2011/03/when-life-gives-you-lemons-make-lemon-curd/