Preheat oven to 350 degrees F. Line a 9x13-inch baking pan with parchment paper.
Add prunes to a saucepan; cover with water and bring to a boil. Remove from heat and let stand for 10 minutes. Strain any excess water. Mash prunes and set aside. In a bowl, stir flour with cinnamon, cloves and nutmeg; set aside. In a separate bowl, beat sugar with eggs and 2 tablespoons butter until blended. In a measuring cup, mix prune juice with 1 tablespoon baking soda. Stir into mixture alternating with flour mixture. Stir in mashed prunes. Transfer to prepared baking pan.
Bake for 30 to 35 minutes or until tester inserted into center comes out clean. Cool for 15 minutes. Remove from pan and cool completely on rack. Meanwhile, prepare the sauce.
Sauce: Add 1/2 cup butter, sugar, syrup, cream and 1/2 teaspoon baking soda to a small saucepan set over medium heat; bring to a boil. Boil for 2 minutes. Cut cake and serve with warm sauce.