Preheat the oven to 350F. Butter a 13x9-inch baking dish or spray with baking spray.
In a large bowl, whisk together the flour, baking powder, and salt.
Separate the eggs into two separate bowls, a medium one for the yolks and a large one for the white. Beat the egg whites on high speed until foamy and doubled in size, about 1 minute. While beating, slowly pour in ¼ cup sugar. Continue beating until stiff peaks form, about 3 minutes.
Add the remaining 1 cup sugar to the egg yolks and beat on medium speed until pale and fluffy, about 1 minute. Beat in the milk and vanilla. Pour into the flour mixture and beat just until combined.
Using a spatula, fold the egg whites into the flour mixture in two batches, until no white streaks remain. Pour the batter into the cake pan.
Bake for 25 to 30 minutes or until a toothpick inserted into the center comes out clean. Let the cake cool until slightly warm. (The cake will fall and shrink as it cools. This is normal!)
For the Syrup:
In a medium bowl, whisk together the condensed milk, evaporated milk, and whole milk until well combined. Poke the cake all over with a fork. Slowly pour the syrup over the cake. Cover and chill for at least 1 hour.
For the Frosting:
In a large bowl, beat the cream and sugar on medium speed until soft peaks form. Spread over the cake. The cake can be covered and refrigerated for 3 days before serving. Garnish with strawberries, if desired.
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Notes
Use a scale to measure the flour. However, if you don't have a scale, be sure to fluff your flour with a spoon and then spoon it into your cups before leveling it off with a knife. This method is the best way to measure flour without overpacking the measuring cup, leading to a dense cake.
Separate the eggs while they are cold. Eggs are much easier to separate when cold, but egg whites whip up easier when closer to room temperature. I recommend separating the eggs in advance if you have the time so that the egg whites can come to room temperature.
When whipping the egg whites, make sure there's no water or oil in the bowl, as it will prevent the egg whites from forming peaks.
Don't deflate the whipped egg whites. When folding the egg whites into the flour mixture, turn the mixture in on itself with a cutting motion, not stirring. This way, you gently incorporate the egg whites and do not deflate them.
Don't overmix the batter. Otherwise, you'll overdevelop the gluten and will end up with a tough cake.
To pop air bubbles in the cake batter: Gently tap the cake pan on the counter a few times to pop any large air bubbles and level out the batter in the pan for an even bake.
Topping ideas: Keep it simple. The sweet whipped cream frosting is enough, but if you like, you can add a sprinkle of cinnamon or sliced fresh strawberries on top.