Combine powdered sugar, zest, and lemon juice in saucepan. If using thyme, add that now as well. Stir to combine and place over medium heat.

Crack eggs into a medium bowl and whisk vigorously until light and frothy, about 1 minute.

When lemon juice mixture is very hot, take a small ladle and slowly drizzle hot mixture into eggs while whisking constantly. Add slowly, one ladle at a time, until it is all combined. Pour this mixture back into the saucepan and cook over medium heat, stirring constantly, until you have a thick, pudding-like consistency that coats the back of your spoon.

Pour mixture through fine mesh strainer set over a clean bowl. Push or whisk mixture through the strainer and discard any solid bits, including thyme, left in the strainer.

Add one small cube of butter at a time, and whisk until it is completely combined before adding another cube.

Once all butter is combined, add 1 tablespoon fresh lemon juice and whisk once more to combine.

Place in jar with tightly fitting lid, or in a bowl covered with plastic wrap. Make sure plastic lies directly against the surface of the lemon curd to prevent a skin from forming.

Store in refrigerator for up to a week.

You can smear this on biscuits, scones, toast, pancakes, waffles, make cookie sandwiches or fill doughnuts. Or you can use it to make the most delicious ice cream. Recipe linked here: Lemon Curd Ice Cream