Preheat the oven to 350°F. Spritz a 13x9-inch baking pan with cooking spray. Set aside.
Cake Batter: Mix together the oats and boiling water in a small bowl. Set aside for 15 minutes to allow the oats to soften and cool.
In a medium bowl, use a whisk to sift together all purpose flour, baking soda, ground cinnamon, salt and nutmeg.
Using an electric mixer on medium speed, cream together butter, evaporated milk, brown sugar, granulated sugar and vanilla extract in a large bowl.
Add the eggs one at a time beating well after each addition.
Add the cooled oatmeal and dry ingredients to the wet ingredients. Continue to beat on medium speed just until fully combined. Stop and scrape the sides of the bowl periodically.
Pour and spread the cake batter into the prepared pan. Bake for 35-40 minutes or until a toothpick inserted into the center comes back with moist crumbs.
Broiled Coconut Icing: Melt butter in a medium size microwave safe bowl.
Add coconut, pecans, brown sugar, evaporated milk, vanilla extract and ground cinnamon. Stir until fully combined.
Spread the coconut-pecan topping onto the top of the cake immediately after it's removed from the oven. Increase the oven setting to broil moving the rack to the upper third of the oven.
Broil for 3-5 minutes until the topping has melted, is bubbly and light golden brown. (Do not walk away the topping can burn easily, if left unattended.)
Cool to warm or serve at room temperature.