Oatmeal Cake With Broiled Icing

1. FOR THE CAKE: Adjust oven rack to middle position and heat oven to 350 degrees. Make foil sling by folding 2 long sheets of aluminum foil so that they are as wide as 8-inch square baking pan. Lay sheets of foil in pan, perpendicular to one another, with extra foil hanging over edges of pan. Push foil into corners and up sides of pan, smoothing foil flush to pan. Spray foil with vegetable oil spray.
2. Combine oats and water in medium bowl and let sit until water is absorbed, about 5 minutes. In another medium bowl, whisk flour, baking soda, baking powder, salt, cinnamon, and nutmeg together.
3. Using stand mixer fitted with paddle, beat butter, granulated sugar, and brown sugar on medium speed until combined and mixture has consistency of damp sand, 2 to 4 minutes, scraping down bowl as needed. Add egg and vanilla and beat until combined. Add flour mixture in 2 additions and mix until just incorporated, about 30 seconds. Add soaked oats and mix until combined, about 15 seconds. Give batter final stir by hand.
4. Scrape batter into prepared pan, smooth top with rubber spatula, and gently tap on counter to release air bubbles. Bake cake until toothpick inserted in center comes out with few crumbs attached, 30 to 35 minutes, rotating pan halfway through baking. Let cake cool slightly in pan, at least 10 minutes.
5. FOR THE BROILED ICING: While cake cools, adjust oven rack 9 inches from broiler element and heat broiler. In medium bowl, whisk together brown sugar, melted butter, and milk, then stir in coconut and pecans. Spread mixture evenly over warm cake. Broil until topping is bubbling and golden, 3 to 5 minutes.
6. Let cake cool in pan on wire rack for 1 hour. Remove cake from pan using foil and transfer to platter. Gently push side of cake with knife and remove foil, 1 piece at a time. Serve.

Do not use old-fashioned or instant oats for this recipe. Be sure to use a metal baking pan; glass pans are not recommended when broiling. If you have a drawer-style broiler (underneath the oven), position the rack as far as possible from the broiler element and monitor the icing carefully as it cooks in step 5. A vertical sawing motion with a serrated knife works best for cutting through the crunchy icing and tender cake.