Preheat the oven to 175°C (350°C) and grease a 9-inch by a 13-inch baking pan with butter and lightly dust the bottom and sides with flour.
Combine the flour, salt, and baking powder and sift into a bowl and whisk together. Set aside.
Add the egg white into a clean dry mixing bowl and beat on medium-low speed until egg white reaches soft peaks.
With the mixer running, gradually add the sugar and beat on medium speed until still peaks are formed about 5 minutes.
Reduce the mixer speed to low and add the egg yolks one at a time making sure each egg yolk is combined in between each addition.
Add the flour in portions alternating with the milk and fold into the egg white mixture with a spatula. Once mixed add the vanilla extract and mix to combine.
Pour the sponge cake batter into the greased baking pan and using a spatula spread until even.
Bake for 25 -30 minutes or until the center comes out clean when inserted with a toothpick.
In the meantime, combine the heavy cream, sweetened condensed milk, and evaporated milk into a blender and mix until well combined. Alternatively, you can mix with a whisk.
Once the cake is baked, remove it from the oven, pour 1/2 of the tres leches cream on top of the cake while the cake is hot, allow it to absorb a few minutes, then add the remaining cream mixture.
Allow the cake to seep and cool completely at room temperature for 40 minutes.
Placed covered in the refrigerator for at least 2 hours.
Prepare the meringue icing: Add the sugar and water into a medium-size saucepan and bring to a boil on medium-high heat.
Reduce the heat to medium-low heat and stir, continue to cook the sugar mixture until it reaches 113-115°C (235-240°F), soft ball stage, then remove from the heat.
Place the egg whites into a clean dry bowl and beat using a hand mixer on slow speed or whisk until soft peaks form, while beating, carefully and slowly add the hot sugar syrup and continue to beat until the mixture is well combined.
The meringue frosting will begin to thicken with a glossy finish once it cools down.
Remove the tres leches cake from the refrigerator and cover the top with the meringue icing. Sprinkle the top with some cinnamon or garnish with fresh fruit.
Serve and Enjoy!