Heat oven to 350˚F. Grease a 9-inch x 13-inch pan. Get out a big mixing bowl.
Put the dry ingredients in the bowl first, and stir well to mix them. Add the oil, applesauce, and eggs; beat until well combined. Add the raisins last, and stir them to distribute them evenly.
Pour batter into prepared pan. Bake at 350˚ 35-40 minutes. A toothpick inserted toward the center of the cake should come out without any crumbs.
Let the cake cool on a rack.
FOR THE ICING
The cake must be completely cool before you put icing on it (buttercream will melt on a warm cake!) A quick check: if you can rest the cake pan on your open palm and it doesn’t feel warm, the cake is cool enough.
Mash the butter, add powdered sugar (if you’re feeling fancy sift the sugar first). Add vanilla extract, beat again. We prefer a thin glaze, rather than a thick coat of frosting. If you like a fluffier thicker frosting, double the amount.
NOTE: for a smaller cake, cut all ingredients in half, and bake in an 8x8 pan