Cake:
Nonstick cooking spray
1¼ c. boiling water
1 c. old-fashioned rolled oats, uncooked
1½ c. all-purpose flour
1 tsp. baking soda
1 tsp. ground cinnamon
½ tsp. ground nutmeg
½ tsp. kosher salt
½ c. salted butter, softened
1 c. granulated sugar
¾ c. packed light brown sugar
2 tsp. vanilla extract
2 large eggs, at room temperature
Topping:
6 Tbsp. salted butter
½ c. packed light brown sugar
1/3 c. sweetened condensed milk
1½ c. sweetened flaked coconut
¾ c. pecans, toasted and chopped
Preheat oven to 350°. Spray a 13x9 broiler-safe pan with nonstick spray. In a heat-proof bowl, stir the boiling water and rolled oats together. Let sit for 30 minutes, stirring occasionally, until softened.
In another bowl, whisk the flour, baking soda, cinnamon, nutmeg and salt. In a stand mixer with the paddle attachment, cream the butter, granulated sugar, brown sugar and vanilla until light and fluffy, 3-4 minutes. Add the eggs, one at a time, mixing thoroughly after each addition.
Add the flour mixture in two batches, then fold in the softened oat mixture. Scrape down the sides of the bowl as needed. Pour batter into the prepared pan. Bake 30-35 minutes, until a toothpick inserted in the center comes out clean. Let the cake cool for 10 minutes.
For the topping, in a heavy-bottomed saucepan, melt the butter, brown sugar and condensed milk over medium heat, stirring constantly until smooth and just simmering. Remove from heat and stir in the coconut and toasted pecans. Spread the mixture evenly over the warm cake.
Switch oven to broil and place the cake on the center rack. Broil for 2-3 minutes, watching carefully as it can burn quickly, until the topping bubbles and turns golden. Allow cake to cool completely before slicing. —15 slices.