Preheat the oven to 350 degrees Fahrenheit.
In a large bowl, combine 1 cup flour, 1 ½ tsp baking powder, and ¼ tsp salt. Use a whisk to combine. Set aside.
In two separate bowls, separate the 5 eggs into egg whites and egg yolks. Set the whites aside.
Add ¾ cup granulated sugar into the egg yolk and use an electric hand mixer to beat until pale and smooth. Add ⅓ cup milk and mix to combine.
Add the egg yolk mixture into the flour mixture and use a rubber spatula to fold the mixtures together. Do this gently and don’t overmix. Set aside.
Use a stand mixer to electric hand mixer to beat the egg whites. When soft peaks form, add the remaining granulated sugar, a little bit at a time. Continue to beat on high until stiff peaks form.
Add the whipped egg whites into the flour and egg yolk mixture and use a rubber spatula to fold them together. Do this gently so as not to deflate the egg whites.
Spray a 9x13 pan with nonstick spray. Then pour the batter into the pan. Bake for 25-30 minutes or until a toothpick inserted into the center of the cake comes out clean. Once baked, allow the cake to cool completely.