Grape-nuts Lemon Pudding

I remember my grandmother making this and it was one of her favorites. I love anything lemony and the grapenuts make it a little crunchy. It is the ultimate comfort food and is well worth the time it takes to bake it.

Cream 1 teaspoon lemon rind and 4 Tablespoons butter. Add 1/2 cup sugar gradually, blending well. Add 2 egg yolks and beat well. Then add 3 Tablespoons of lemon juice. Add 2 Tablespoons flour, 1/4 cup Grapenuts cereal, and 1 cup milk. Mix well. Fold in 2 stiffly beaten egg whites. Turn out into a buttered baking dish and place in a pan of water, about an inch deep. Bake at 325 degrees for 1-1/4 hours. Serve cold.