Whisk: In a large bowl, combine the egg yolks, lemon zest and sugar. Whisk by hand or with an electric mixer until pale and smooth but not frothy.
Thicken: In a medium saucepan on a low heat, melt the butter. Once melted and foaming, add the lemon juice and stir through. Add the egg yolk and sugar mixture to the pan and stir constantly for 7 - 10 minutes with a spatula until it thickens and turns a deep yellow colour. You should be able to coat the back of a spoon with the lemon curd. This tells us it's at the perfect consistency.
Cool: Remove from the heat and allow to cool. Transfer to a sterilised jar and pop into the fridge. Store for up to 2 weeks!
Notes
Store: Transfer to a sterilised jar and pop into the fridge. Store for up to 2 weeks in the fridge. Serve: Serve alongside ice cream, on toast or with my meringue roulade!