You know when a 9×13 cake disappears in one sitting with only four eaters that it has to be good. This is quite fabulous. I think they serve something like this at Cafe Rio, but I’m willing to venture that this is much, much better.
Tres Leches Cake

With a little cinnamon on top, for effect.
2009 America Test Kitchen Yearbook
Milk Mixture
1 (14 oz.) can sweetened condensed milk
1 (12 oz.) can evaporated milk
1 c. heavy cream
1 t. vanilla
Cake
2 c. unbleached all-purpose flour
2 t. baking powder
1 t. salt
1/2 t. ground cinnamon
8 T (1 stick) butter
1 c. whole milk
4 large eggs, room temperature [to do this quickly, you can place cold eggs in warm water while you assemble other ingredients]
2 c. sugar
2 t. vanilla
Frosting
1 c. heavy cream
3 T. light corn syrup
1 t. vanilla extract
For milk mixture: Pour the condensed milk into a large microwave-safe bowl and cover tightly with plastic wrap (if it’s not large enough, the mixture will bubble over. I had multiple problems with this, and recommend using a very large bowl. Tell me if it works). Microwave on low power, replacing the plastic wrap and stirring every 3 minutes. After 9-15 minutes, the mixture should be thicker and darker. In another bowl, combine evaporated milk, cream, and vanilla. Slowly whisk the cooked sweetened condensed milk into this mixture and set aside to cool.
For cake: Preheat oven to 325 and grease and flour a 13×9 baking dish. Combine dry ingredients in a small bowl and set aside. Melt the butter and milk in a small saucepan over low heat. Remove from heat and set aside. In a standing mixer, beat the eggs for 30 seconds, then add the sugar slowly. Increase the speed to med.-high and beat for 6-7 minutes. Reduce speed and add the vanilla, and then the butter mixture. Add the flour in 3 additions, scraping the bowl after each addition. Pour batter into prepared dish, and bake for 30-35 minutes, or until a toothpick comes out clean. Let cool for 10 minutes on a wire rack.
After ten minutes of cooling, use the blunt end of a skewer to make holes about 1/2″ apart all over the cake. Pour the milk mixture slowly over the cake until it is completely absorbed. Let sit at room temperature for 15 minutes, then refrigerate uncovered for at least 3 or up to 24 hours.
For frosting: Beat cream, corn syrup, and vanilla to soft peaks with a mixer. Frost and serve.
Note: I had trouble with the dulce de leche in the microwave, and I would love to hear how it worked for others. I also didn’t frost the cake–it seemed a little like gilding the lily, but perhaps it would just make a great thing even better.