Add all ingredients except for butter and vanilla to the bowl of a large food processor. Pulse for about 15 seconds, just to combine. Add the butter and vanilla and process until the mixture resembles a coarse meal – you want it to look much like a boxed mix would.
Divide the mix equally into two zip-top bags and store in the freezer for up to two months.
To Make the Cake:
Preheat oven to 350°F. Grease and flour the pan of your choice.
Use an electric mixer to beat together one bag of the prepared mix, 1 1/4 cups warm water and 2 large eggs until smooth, about 2 minutes.
Pour into the prepared pans and bake:
about 25 minutes for 9-inch layer cakes
30-35 minutes for a 13x9-inch cake
45 minutes for a bundt cake
18-20 minutes for cupcakes.
A toothpick inserted into the center of the cake should come out clean when the cakes are done.
Notes
To use the mix in a recipe calling for 1 box of cake mix, use about half, or about 3 1/2 cups, of the prepared mix.Makes the equivalent of approximately two boxed cake mixes.