Preheat the oven to 350 degrees F (175 degrees C). Grease three 8 or 9 inch round cake pans and set aside.
In a large bowl, beat butter and sugar until light and fluffy. Add eggs one at a time, mixing until each one is blended in. Dissolve the baking soda in the water; stir into the batter along with the blackberry jam. Combine the flour, cloves, nutmeg, cinnamon and salt; stir into the batter by hand, alternating with the buttermilk. Fold in the black walnuts and raisins if using. Divide the batter equally between the three pans, and spread in an even layer.
Bake in the preheated oven until the top of the cakes spring back when lightly touched, about 35 minutes. Cool in the pans until cool enough to handle, then invert the cakes over a wire rack and remove pans to cool completely.
