vegetable oil, plus more for panAll-purpose flour (for pan)Homemade Yellow Cake Mix3 large eggs1/2 teaspoon vanilla extract2 cups favorite frostingPreparation Preheat oven to 350°F. Grease and flour a 13x9" baking dish. Using an electric mixer on medium speed, beat cake mix, eggs, vanilla, 1/3 cup oil, and 1 cup water in a large bowl until combined, about 2 minutes. Pour batter into prepared pan. Bake cake until surface springs back to the touch and cake is set and golden brown, 25–30 minutes. Let cool completely, then turn out onto a platter before frosting. Do Ahead Cake can be made 3 days ahead; store at room temperature.