Preheat oven to 350˚F. Grease an 8×8 square pan or something else of equivalent size.
Put the dry ingredients in a large bowl, and whisk them well together. Combine the wet ingredients in a large measuring cup, and then quickly stir them into the dry and mix well, until very smooth. Work fast! Speed is important for this cake.
NOTE: you can put the mixed dry ingredients in a greased pan, make 3 wells, put oil, vinegar, and vanilla in each, then pour water over and mix rapidly with a fork – but I like mixing in the bowl better, I can do that faster, and there are no corners to blend.
Dump the batter in your prepared pan, and get it right into the oven. Bake about 30 minutes for an 8×8 square pan, 22-24 minutes for cupcakes. Test as usual: the cake should spring back in the center when lightly touched, the edges should be pulling away from the pan, and a toothpick inserted in the center should come out moist but with no streaks of raw batter. Let stand on a rack to cool.