Preheat the oven to 350 degrees Fahrenheit. Grease a 9×13-inch cake pan.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a large bowl, beat the egg yolks with 3/4 cup of white sugar until fluffy. Stir in the vanilla extract.
Gradually add the dry ingredients to the egg yolk mixture, alternating with the milk. Mix until well combined.
In a separate bowl, beat the egg whites until foamy. Gradually add the remaining 1/4 cup of sugar and continue beating until stiff peaks form.
Gently fold the beaten egg whites into the cake batter until fully incorporated.
Pour the batter into the prepared cake pan and bake for about 30 minutes, or until a toothpick inserted into the center comes out clean.
In a large measuring cup, whisk together the whole milk, sweetened condensed milk, and evaporated milk.
Once the cake is cooled to room temperature, poke holes all over the top with a fork. Pour the milk mixture over the cake, allowing it to soak in evenly.
Cover the cake and refrigerate for at least 4 hours or overnight to allow the flavors to meld.
Before serving, prepare the whipped cream topping. In a large mixing bowl, beat the heavy cream, powdered sugar, and vanilla extract until soft peaks form.
Spread the whipped cream over the chilled cake.
Serve the Tres Leches Cake with a sprinkle of cinnamon or fresh fruit, if desired.
Store any leftovers in the refrigerator for up to 4-5 days, but it’s best enjoyed within 48 hours.