Lemon curd is made with lemon juice, sugar, butter and egg yolks. The mixture is cooked until it is thick and creamy. In England, lemon curd is a traditional topping for scones. Look for lemon curd in the gourmet-food section or near the jams in your supermarket.
One cup of frozen whipped topping, thawed, can be used in place of the whipping cream and powdered sugar.
Assemble these lovely tartlets and refrigerate, uncovered, for up to 4 hours.