Cream brown sugar and butter together until fluffy, add egg and beat well. Sift flour, measure and resift with soda, cinnamon, cloves, and salt. Wash raisins letting them soak in water for a few minutes, then squeeze dry. Dredge raisins with 1 cup flour mixture, add remaining flour to butter mixture alternately with the buttermilk. Stir after each addition until smooth. Add raisins and mix gently but well. Add vanilla and rum. Grease 2 (9-inch) layer pans. Bake in moderate oven 375° F. for 20 minutes, until done. Remove from oven. Invert pans onto cake rack and allow layers to cool. When completely cold, fill and frost.
For filling: Combine sugar, sour cream and salt and cook slowly, stirring until thick. Remove from fire, cool slightly and add nuts and rum. Spread between layers and frost with caramel frosting.