Preheat the Oven:
Preheat your oven to 350°F (175°C). Grease and flour a 9x13-inch baking dish.
Prepare the Cake Batter:
In a medium bowl, whisk together the flour, baking powder, and salt.
In a large bowl, beat the egg yolks with ¾ cup sugar on high speed until the yolks are pale yellow. Stir in the milk and vanilla extract.
Gently fold the flour mixture into the yolk mixture until just combined.
In a separate bowl, beat the egg whites on high speed until soft peaks form. Gradually add the remaining ¼ cup sugar and continue beating until stiff peaks form.
Gently fold the egg whites into the batter until fully incorporated.
Bake the Cake:
Pour the batter into the prepared baking dish and spread it evenly.
Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 30 minutes.
Prepare the Tres Leches Mixture:
In a medium bowl, whisk together the sweetened condensed milk, evaporated milk, and heavy cream.
Once the cake has cooled, poke holes all over the surface using a fork or a skewer.
Slowly pour the milk mixture over the cake, allowing it to soak in. Let the cake absorb the milk mixture for at least 1 hour in the refrigerator.
Garnish and Serve:
Garnish with fresh berries or a dusting of cinnamon or cocoa powder, if desired.
Slice and serve chilled.