Chocolate Mayonnaise Cake

2 cups all purpose flour
1 1/2 cups white sugar
1/4 cup unsweetened cocoa powder
1/8 tsp. salt
2 tsp. baking soda
1 cup water
1 tsp. vanilla extract
1 cup mayonnaise

Preheat oven to 375F. Grease and flour a 13x9-inch pan.
Mix together dry ingredients; make well in center.
Add water, vanilla, and mayonnaise; beat with whisk.
Bake at 375F 40-50 minutes.