This moist cake gets even better when served with vanilla ice cream or a dollop of whipped cream.
Adjust oven rack to middle position and heat oven to 350 degrees.
Coat 8-inch-square baking pan with nonstick cooking spray.2.
Whisk flour, sugar, cocoa, baking soda, and salt together in pan.
Make one large and two small craters in dry ingredients.
Add oil to large crater and vinegar and vanilla separately to remaining small craters.
Pour water into pan and mix until just a few streaks of flour remain.
Immediately put pan in oven.3.
Bake until toothpick inserted in center of cake comes out with a few moist crumbs attached, about 30 minutes.
Cool in pan, then dust with confectioners' sugar.
(If tightly wrapped, cake will keep for three days at room temperature.)