Melt 2 Tablespoons butter in 10-inch skillet over medium heat; add oats and toast until golden brown. Add boiling water to oats, and let sit 20 minutes.
Preheat oven to 350°F.
Butter 9x13 inch metal pan.
Whisk together flour, baking soda, salt and cinnamon; set aside.
Cream ½ cup butter and sugars. Beat in eggs one at a time until mixture is light and fluffy. Stir in flour mixture alternately with oatmeal mixture.
Pour batter into prepared pan.
Bake 30 minutes or until center tests done. Remove from oven.
Preheat oven to broil.
Combine topping ingredients in a pan over low heat and spread over warm cake.
Place about 5 inches below the heat source and broil until topping is brown and bubbly (about 2 minutes - watch carefully to avoid burning).