-if desired Pour water over dates and soda; let stand until lukewarm. In bowl, cream butter with sugar; beat in egg and vanilla. Mix together flour, baking powder and salt; add to creamed mixture alternately with date mixture. Spread in a greased and floured 9 inch square cake pan. Bake in 350F oven for 40 minutes or until tester comes out clean. BROILED TOPPING: In a small heavy saucepan, combine butter, packed brown sugar, light cream and coconut (half nuts if desired). Bring to a boil, stirring; boil gently for 1 minute. Spread over warm baked cake; broil until bubbly and lightly browned, watching carefully.