This is what my research has told me is a traditional Tres Leches cake. A lean sponge cake as the base instead of the usual American version using a butter cake, and plenty of milk to soak it in. It's a pretty quick cake to put together, but it's best if you let it soak overnight. You could just serve it naked, but I like to make a quick whipped cream with 2 cups of heavy whipping cream, 2 tbsp of sugar, and 1 tsp of vanilla extract to frost it (I strongly suggest this way of serving it! Who doesn't love whipped cream) —Taylor Ayral
Preheat an over to 350 F. Grease a deep 9x9" cake pan very well with non-stick spray, then place a sheet of parchment paper on the bottom, cut long enough so that it hangs over two of the sides of the pan and can be used to lift the cake out of the pan. Grease the parchment paper as well.
Using an electric mixer or stand mixer with the whisk attachment, whip the egg whites until frothy. With the mixer still on high, slow all but 2 tbsp of the sugar. Beat until the white attain stiff peaks (it's preferable to go a little under than over.)
In a separate, clean bowl, beat together the egg yolks, remaining sugar, and vanilla, until thick and very light in color. You want them to be thick enough that the yolk that falls off the beaters stays visible for a few seconds before sinking into the bowl. Using an electric mixer makes things easier.
Combine the flour, baking soda, and salt in a bowl, whisk to combine.
Carefully pour the whipped yolk mixture on top of the whipped egg whites. Using a spatula, fold the yolks into the whites using gentle, folding and rotation motions. Try not to deflate the foam.
Gently add the flour mixture to the foam in 3 additions, folding until almost completely incorporated before adding the next addition. Once everything is combined you should have a very sticky batter.
Transfer to the prepared pan. Bake on rack in the center of the over until a toothpick inserted in the center comes out clean and fairly dry, about 22-25 min. Cake should be lightly browned on the top and spring back when you gently touch the middle. Allow the cake to cool completely.
Combine the sweetened condensed milk, the evaporated milk, the half & half, and the orange liqueur in a large container with a spout for pouring. Mix to combine.
Once the cake is cool, gently use your hand to coax the edges of the cake to pull off the pan. If this isn't happening, run a thin knife along the sides.
Pour about 3/4 of the milk mixture over the cake, trying to pour over every part of the top. Allow the cake a few minutes to absorb and use your judgment as to whether or not to pour over the rest of the milk. This cake is basically a giant sponge, and can absorb a lot more liquid than you think, but how much it wants to drink will depend on how dry you baked it. I generally end up with about 2-4 tbsp of milk left.
Cover, and allow to soak in the refrigerator over night.
Use the edges of parchment paper to remove the cake from the pan. Be gentle; the cake should hold together but it will be soggy. If it doesn't look like it'll make it without falling apart, just leave it in the pan and cut your slices out of there.
If desired, frost with a nice thick layer of fresh whipped cream, and garnish with fresh fruit. Last time I did it, I used candied limes, strawberries, and cocoa powder to make it look like the Mexican flag. Be creative.
Or, just enjoy this deliciously moist, slightly sticky, perfectly sweet cake naked and proud. The cake, I mean.