Preheat your oven to 350°F. Grease and flour a 9x13-inch baking pan.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a large bowl, beat the egg yolks with ¾ cup of sugar on high speed until the yolks are pale yellow. Stir in the milk and vanilla.
Pour the egg yolk mixture into the flour mixture and gently mix until combined.
In a separate bowl, beat the egg whites on high speed until soft peaks form. Gradually add the remaining ¼ cup of sugar, beating until stiff peaks form.
Gently fold the egg whites into the batter, being careful not to deflate them.
Pour the batter into the prepared baking pan 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 completely.