Heat oven to 350°F. In medium bowl, mix flour, 3/4 cup sugar, 1/4 cup cocoa, the baking powder and 1/2 teaspoon salt. Stir in milk, butter and vanilla until well blended. Spread batter in ungreased 8-inch square or 9-inch round cake pan.
In small bowl, mix 1 cup sugar, 1/4 cup cocoa and dash salt. Sprinkle evenly over batter. Pour boiling water over sugar mixture.
Bake 40 to 50 minutes or until center is set and firm to the touch. Serve warm. If desired, serve with ice cream. Store in refrigerator.