I just posted two great recipes that take only two or three ingredients and they are super good.

Here is a link that might be useful: 2- 3 ingred cupcakes

Most bakeries (gasp!) use box mixes, doctored.

I sell cakes professionally, and do a bit of both. My chocolate, red velvet, carrot, and other speciality flavored cakes are scratch.

My white, yellow, lemon, coconut are doctored. I add the following to a box of cake (usually DH but you can use any of the brands), and DO NOT add the ingredients listed on the boxes instructions:

1 cup of sour cream
a box of pudding (unless carving, then it's too moist)
1 cup sugar
1 cup flour
3 eggs
1/4-1/3 cup oil (eyeballed)
1 cup water (or milk or coffee creamer in coordinating flavor)
2 tsp vanilla (or coordinating flavored extract)

For cupcakes, preheat to 400 degrees and when you put them in decrease it to 325. That gives it the nice 'muffin' top. If baking a cake, keep it at 325.

You can use lemon cake w/ lemon pudding, yellow cake w/ vanilla pudding and so on. They're delicious.