In those pastry recipes, I’d commented on Crisco and Spry, which are hydrogenated vegetable fats, and Spry is also one of the ingredients for the lemon curd here. Spry can be substituted here with butter, which probably also gives a better taste.
Cooking the curd in a pan of simmering boiling water rather than over direct heat helps to prevent the eggs from curdling. Read more about this technique and tips on making lemon curd here. If curdling does happen, the lemon curd will have to be strained, so this alternative recipe suggests a way to avoid the problem (including a fascinating scientific explanation) as well as more tips for getting a successful lemon curd.