Dissolve soda in hot water and let stand until cool. Sift dry ingredients together. Mix all ingredients adding the soda water last. Batter will be thin. Bake at 350F for 40-45 minutes.
To make fudge frosting: Combine all ingredients in a pot and stir over low heat until melted. Stir constantly bringing rapidly to a full boil and boil for 1 minute. Cool until lukewarm. Add 1 tsp. vanilla and beat until it is of spreading consistency.