Preheat the oven to 350°. Grease a 9x13 pan and set it aside.
In a medium bowl add the oats and boiling water. Let stand while the rest of the batter is prepared.
In a large bowl beat the butter and both sugars on medium high until light and fluffy. Add the eggs and mix until combined.
In a medium bowl whisk together the flour, baking soda, salt, cinnamon, and nutmeg together. Add the flour mixture to the butter mixture and mix until combined. Add the vanilla and soaked oats. Mix until combined.
Pour the batter into the prepared baking pan and bake for 30-40 minutes, until a toothpick comes out clean from the center of the cake.
While the cake is baking, prepare the frosting by stirring together the melted butter. milk, vanilla, brown sugar, coconut, and pecans. Once the cake has finished baking, pour the frosting over the hot cake.
Switch the oven to the broiler and broil the frosted cake for 1-2 minutes, just until the edges of the coconut start to toast. This happens quickly, so don’t walk away from the oven while it broils.
Let the cake cool for 20-30 minutes before slicing and serving. You may also cool the cake completely before serving.