Cream butter, sugar, and eggs. Fold in molasses. Add flour, buttermilk and spices with soda alternately, stirring well after each addition. Put into a square pan and bake in a 350 degree oven for 25 minutes. Dust with powdered sugar.
In a saucepan, put ½ cup sugar and 1 teaspoon cornstarch. Slowly add 1 cup of water. Cook over low flame for 5 minutes or until thickened. Stir in 3 tablespoons butter, 1 teaspoon lemon zest and 3 tablespoons fresh lemon juice, also ⅛ teaspoon salt. Serve cold or hot. You can fold in 1 cup of whipped cream if serving cold.