This came from http://www.allrecipes.com/ and you can print a "pretty version" (complete with conversions if needed) here. Yes, this does call for vinegar and mayonaise . . . but it is sooo good! Top with chocolate frosting (home-made of course) and you are in heaven!
"Aunt Joyce's Chocolate Cake"
3 (1 ounce) squares unsweetened chocolate, chopped
1 cup mayonnaise
2 tablespoons vinegar
2 tablespoons vanilla extract
3 cups all-purpose flour
2 cups white sugar
2 teaspoons baking soda
1 teaspoon salt
2 cups warm water
Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan. Melt the chocolate in a double boiler or in the microwave.
Pour the melted chocolate into a large mixing bowl. Blend in the mayonnaise, vinegar and vanilla. Combine the flour, sugar, baking soda, and salt and gradually stir into the chocolate mixture. Slowly stir in the warm water. Pour batter into prepared pan.
Bake in the preheated oven for 30 to 35 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool.
Note: The cake batter looks like soup . . . . don't worry . . . . it will turn out very well!