For 4 Person(s)
Preparing lentil purée: Add 2 ½ times the amount of water as lentils. Bring to a boil, reduce heat, cover and simmer for 45 minutes. Stir frequently. Cool slightly and do not drain. In small batches, mash or purée lentils with a sieve, food mill, blender, food processor or potato masher. Purée should be the consistency of canned pumpkin. Add water to thin if needed.
Preheat oven to 350°F.
Stir together boiling water, oatmeal and butter. Let stand until margarine melts. Mix with remaining cake ingredients.
Pour batter into a greased and floured 13 x 9-inch baking pan and bake for about 45 minutes or until cake springs back when lightly touched. Cool slightly in pan.
Heat all topping ingredients in a saucepan; do not boil.
Spread topping evenly over the cake. Place it under broiler, 4 to 6 inches from heat, and broil until topping is hot and slightly brown. Watch very carefully to avoid burning.