Heat oven to 350°F.
Place dates into bowl; add boiling water. Set aside.
Combine sugar and 1/4 cup butter in another bowl; beat at medium speed, scraping bowl often, until creamy. Add egg and vanilla; continue beating until well mixed. Add flour, baking powder and salt; beat at low speed until well mixed. Stir in date mixture until well mixed.
Pour batter into greased 9-inch round baking pan. (Batter will be thin.) Bake 35-40 minutes or until toothpick inserted in center comes out clean. Poke top of hot cake 10-15 times with fork.
Melt 1/3 cup butter in 1-quart saucepan. Add brown sugar and 1/3 cup whipping cream; cook over medium heat, stirring occasionally, 3-4 minutes or until mixture comes to a boil. Boil 1 minute.
Pour 1/4 cup sauce over top of warm cake. Serve cake warm with remaining sauce, if desired.
Always use the pan size specified in a recipe. A pan too large will result in a thin, dry cake. A pan too small will not be large enough to hold the batter as it expands during baking and the cake will overflow in the oven. To substitute a different pan, check to make sure it holds the same volume as the pan called for in the recipe. For example, in this recipe an 8-inch square baking pan may be substituted for the 9-inch round baking pan.