An oatmeal spice cake with brown sugar icing as sensational as Elvis Presley was.
Preheat oven to 325 F.
In a large bowl, pour the boiling water over the butter or margarine then add brown sugar, and oats and mix until combined. You may use a mixer to make it easier or by hand is fine.
Stir in eggs and vanilla.
In a medium bowl, combine flour, cinnamon, allspice, and baking soda. Add to oat mixture and stir until just mixed.
Pour into a greased and floured 9x13 inch baking pan. Bake in preheated oven for 30 minutes or until toothpick inserted in the centre comes out clean.
Frost with brown sugar icing while still warm. Let cool completely.
Store covered at room temperature up to 3 days, in the fridge up to a week, or in the freezer for up to 3 months.