Add all dry ingredients into a quart-sized Mason jar.
Add a two-piece lid and label and date the jar.
Preheat the oven to 350°F.
In a large bowl, combine eggs and vanilla.
Add dry cake mix ingredients and stir to combine.
Add softened butter and milk and stir until smooth.
Pour batter into greased and floured pans. (Recipe makes one 9-inch square cake or 12 cupcakes.)
Bake at 350°F for 30 to 40 minutes or until a toothpick inserted in the center comes out clean. Bake cupcakes for approximately 16 minutes.
Allow to cool completely before frosting.
