In a large bowl, whisk the flour, sugar, baking powder, and salt together until well-combined.
Add the shortening and vanilla.
Use an electric mixer on low speed to mix everything together. The mixture will be in small crumbs once combined.
Store the cake mix in a large resealable bag or large glass jar with a tight-fitting lid in a cool, dry place for up to 3 months.
To Bake a Cake
Preheat oven to 350F. Grease a 9x13-inch baking pan or 2 9-inch round baking pans. Set aside.
Add the cake mix to a large bowl.
Add eggs, milk, and oil to the cake mix.
Mix with an electric mixer on low speed for 30 seconds.
Increase speed to medium, and continue to mix for 1 minute, scraping down the bowl as needed.
Spread the batter in the prepared baking pan.
Bake until a toothpick inserted in the center comes out clean. For a 9x13 pan, it will take approximately 30-35 minutes. For the 9-inch round baking pans, it will take approximately 25-30 minutes.
Notes
Milk: You can use any dairy milk from skim milk to whole milk. Nondairy milk, like almond milk, will also work in this recipe.
Vegetable oil: A similar oil, like canola oil, will work in this recipe.
Variations
Spice cake: Add 1.5 tablespoons of pumpkin pie spice to the flour.
Confetti cake: Add 1/2 cup rainbow sprinkles to the finished cake mix.
Almond cake: Decrease the vanilla to 1/2 teaspoon. Add 1 teaspoon almond extract along with the vanilla.
Nutrition values are estimates. Nutrition values given are for 1 serving of prepared cake.