Steaming lemon curd is the easiest way I've ever found to make it. It needs minimal stirring and results in the silkiest sweet-tart curd ready for filling pies and cakes or dolloping over ice cream.
Put all the ingredients into a heatproof bowl. I like a Pyrex one because I can see everything that’s going on. I don’t usually recommend glass for steaming because it conducts heat poorly around the food, but it’s going to be in there for a while so it’ll get up to temperature fine. Whisk to combine well, but don’t worry if the melted butter seems to settle on top when you stop whisking. It’ll sort itself out later.
Put bowl into your steam oven and set to 175°F/80°C, steam setting (full steam/100% humidity). There’s no need to cover the bowl. Steam the curd for 15 minutes, then stir well and return to the oven for a further 10 minutes or until thickened to your liking. The curd will noticeably thicken when the overall temperature reaches about 170°F/76°C, and continue to do so up to the oven’s temperature of 175°F/80°C.
When the curd is done, pass it through a fine mesh strainer set over a bowl or jug, before storing in a well-covered container or lidded jar in the refrigerator (if it’s not well-covered it will pick up ‘fridge smell’ very easily).
Notes
These quantities make a very sharp lemon curd, which I love. If you’d prefer yours to sit more on the sweet end of the scale, reduce the lemon juice down to half a cup.
You can increase the quantities of this recipe without much trouble at all. I’ve gone up to a quadruple batch and the only difference was that it took about 10 extra minutes in the oven.
I’ve given directions below to strain the curd after cooking. If you’re not bothered by the possibility of a tiny fleck of cooked egg white or bits of zest in your finished curd, you don’t have to bother, though I really prefer the smoothness of the strained version.
Cooked lemon curd will keep, covered in the refrigerator, for about a week. I’m told it freezes well, though it has never once lasted long enough for me to test that out. If you freeze it, you’ll want to give your curd a good stir after thawing.