I found this recipe on the Target.com recipe page as submitted by Ginger P., and it is excellent - very lemony and a nice contrast to the bread pudding! I love the Bread Pudding with Vanilla Sauce recipe as printed in January 1997 Southern Living. I always have to make both sauces, though, since we've tasted the lemon sauce in this recipe. We love them both!
In large saucepan, stir together sugar, cornstarch, salt and nutmeg. Gradually stir in boiling water, then simmer over low heat until thick, stirring occasionally.
Remove from heat; stir in butter, lemon zest and lemon juice.
Serve warm over bread pudding (recipe from Southern Living, January 1997).