As someone whose greatest fear in life is dry cake, Tres Leches Cake holds a special place in my heart, as it is impossible not to be dry. While its exact origins are unknown, it is popular all over Latin America, especially in Mexico and Nicaragua, and I fell in love with it through my husband’s love of Mexican food. This version has toasted coconut and lime, two flavors that go deliciously with the milky creamy flavors of Tres Leches cake.
For the cake: Preheat the oven to 350 degrees F. Grease the bottom of a 9-by-13-inch baking pan with cooking spray. Set aside.
Whisk together the flour, baking powder, salt and cinnamon in a medium bowl. Set aside.
Beat the egg whites in a stand mixer fitted with a whisk attachment on medium speed until foamy, about 1 minute. With the mixer still on, slowly add 1/4 cup granulated sugar. Continue until shiny medium-stiff peaks form, about 2 minutes. Remove the egg whites to a medium bowl and set aside.
Add the egg yolks and remaining 3/4 cup granulated sugar to the same bowl of the stand mixer with the same whisk attachment (no need to wash). Beat on medium speed until pale yellow and doubled in volume, 1 to 2 minutes. Add the milk and vanilla, then the lime zest and coconut, beating constantly. Reduce the speed to low and add the flour mixture until just combined.
Using a rubber spatula, gently fold the egg white mixture into the batter in 3 additions until the egg whites are no longer visible.
Pour the batter into the prepared pan and bake until a tester comes out clean, 18 to 20 minutes. Transfer the pan to a rack and let cool slightly.
For the tres leches: Whisk together the sweetened condensed milk, evaporated milk and whole milk in a large measuring cup with a spout. Using a round metal skewer or a fork, poke holes all over the top of the cake, but don't go all the way down to the bottom (this will help the cake absorb the milk!). Pour the milk all over the cake very slowly and a little at a time (this will help distribute the milk throughout the cake). When all of the milk has been poured into the cake and absorbed, cover and refrigerate 2 to 3 hours, preferably overnight.
For the topping: Combine the heavy cream, powdered sugar, cinnamon and salt in a stand mixer fitted with the whisk attachment. Beat on medium-high speed until soft peaks form, 1 to 2 minutes. Dollop, then spread over the top of the cake. Sprinkle with the coconut, then then the lime zest. Cut into 15 rectangles. Serve immediately or store in the refrigerator.