For the Cake
• 1 cup quick cooking oats (not old-fashioned or instant)
• 3/4 cup water, room temperature
• 3/4 cup unbleached all-purpose flour
• 1/2 teaspoon baking soda
• 1/2 teaspoon baking powder
• 1/2 teaspoon salt
• 1/4 teaspoon ground cinnamon •
• 4 tablespoons unsalted butter, softened
• 1/2 cup granulated sugar
• 1/2 cup light brown sugar
• 1 large egg, room temperature
• 1/2 teaspoon vanilla extract
For the Broiled Icing
• 1/4 cup packed light brown sugar
• 3 tablespoons unsalted butter, melted and cooled
• 3 tablespoons milk
• 3/4 cup sweetened, shredded coconut
• 3/4 cup chopped pecans
Preheat oven to 350° F, with rack in the middle position. Spray an 8×8 inch baking pan with nonstick cooking spray and line the pan with two 16-inch pieces of foil, each of which has been folded in half lengthwise. The bottom of the pan should be covered with overlapping pieces and the foil should hang over two opposing sides of the pan. Spray the foil lightly with cooking spray.
Combine the oats with the water in a small bowl until the water is absorbed, about 5 minutes. In a medium bowl, whisk the flour, baking soda, baking powder, salt, and cinnamon together. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugars on medium speed until combined and the mixture has the consistency of damp sand, 2 to 4 minutes. Scrape down the bowl as needed. Add egg and vanilla and beat until combined, about 30 seconds. Add the flour mixture in two additions and beat until just incorporated, about 30 seconds. Add soaked oats and mix until combined, about 15 seconds. Give the batter a final stir with rubber spatula to be sure batter is thoroughly combined.
Transfer batter to prepared pan and lightly tap against counter 3 or 4 times to dislodge any large air bubbles; smooth surface with spatula. Bake until cake tester inserted into center comes out with few crumbs attached, 30 to 35 minutes. Let cool slightly in pan, at least 10 minutes.
While cake cools. adjust oven rack about 9 inches from broiler element and heat broiler.
In a medium bowl, whisk brown sugar, melted butter, and milk together; stir in coconut and pecans. Spread mixture evenly over warm cake. Broil until topping is bubbling and golden, 2 to 5 minutes.
Let cake cool for 1 hour, transfer cake to serving platter and carefully slide the foil out from under the cake. Cut cake into squares and serve.
***Placed in an airtight storage container, this keeps well for several days at room temperature