My favorite recipe is in the old Betty Crocker Cookbook and is listed at Rhubarb Custard Pie. I use only one crust, and substitute any tart or sour fruit in place of the rhubarb, such as gooseberries, etc.
The ingredients are: Beat slightly-3 eggs, then add 2 2/3 T milk. Mix together and stir in 2 cups sugar, 4 T flour, and 3/4 t nutmeg.(In cherry pie ,I substitute 1/3 t almond flavoring.) Add 4 cups fruit . Pour into prepared crust and dot with butter-1 T. Bake at 400 degrees for 50-60 minutes