Grease a 9×13-inch cake pan with butter or oil spray.
In a bowl, whisk together flour, baking powder, and salt.
Separate the egg whites from the yolks. In a large bowl, beat the yolks with 3/4 cup of sugar until pale and fluffy.
Mix in the milk and vanilla extract.
Gently fold in the flour mixture.
In another bowl, beat the egg whites with the remaining 1/4 cup of sugar until stiff peaks form.
Fold half of the beaten egg whites into the batter, then fold in the rest until smooth and fluffy.
Pour the batter into the prepared pan and bake for 30-35 minutes, until a toothpick inserted comes out clean.
Let the cake cool for 30 minutes, then prick the top with a fork.
#### Milk Mixture
In a large measuring cup or bowl, combine evaporated milk, sweetened condensed milk, and heavy cream. Whisk until fully mixed.
Pour the milk mixture over the cooled cake, cover with plastic wrap, and refrigerate for a few hours or overnight.
#### Whipped Cream
In a bowl, whip the heavy cream and powdered sugar on medium speed until soft peaks form.
Add vanilla extract and mix to combine.
Spread or pipe the whipped cream over the cake and sprinkle with cinnamon.
#### Marshmallow Frosting
In a heatproof bowl, combine egg whites, sugar, cream of tartar, and salt. Place over a pot of simmering water and whisk until the mixture reaches 140°F.
Remove from heat and whip with a hand mixer or in a stand mixer until stiff peaks form and the mixture is thick and glossy.
Add vanilla extract and mix well.
Spread or pipe the frosting over the cake. Toast with a kitchen torch or under a broiler for 1-2 minutes.
Notes
Store the Tres Leches Cake in the fridge for up to 4 days.
For stabilized whipped cream, melt 1 tsp unflavored gelatin in 1 tbsp hot water and add to the whipped cream after soft peaks form.
Serve with fresh berries if desired.
Resting the cake in the fridge for at least 12 hours improves the consistency.
If you can’t find evaporated milk, use regular milk or mix 1.25 cups water with 1 cup powdered milk.
Substitute heavy cream with milk or half-and-half if needed.