Chocolate Mayonnaise Cake

I know, this sounds weird, but it is AMAZING!  It's so dark and rich and moist, that it needs no frosting.  You could dust it with some powdered sugar right before serving, though.  That's pretty.

Makes one 13x9 inch cake or two 9 inch round layers.

Have all ingredients at room temp.  Preheat oven to 350F.  Grease and flour a 13x9 inch pan or two 9 inch round pans, or line the bottoms with wax or parchment paper.

Whisk together in a medium bowl:
2 cups flour
1 tsp baking soda
0.5 tsp baking powder

Melt:
4oz unsweetened chocolate, chopped

Set aside.  Beat in a large bowl at medium-high speed until light, about 3 minutes:
3 large eggs
1.66 cups sugar
1 tsp vanilla

Mix the melted chocolate until smooth with:
0.75 cup mayonnaise

and beat into batter.  On low speed, add flour mixture in 3 parts, alternating with:
1.33 cups water

in 2 additions, beating until smooth.  Scrape the batter into the prepared pan(s).
Bake until a toothpick inserted in the center comes out clean, 30 to 40 minutes.  Let the 13x9 cake cool on a rack in the pan, if desired, or cool and remove from the pan.
Dust with, if desired:
confectioner's sugar or cocoa.