In a small bowl, combine butter and brown sugar. Spread over bottom of lightly greased slow cooker. Arrange pineapple on top.
To make cake: In a bowl, combine flour, baking powder and salt. In a large bowl, using an electric mixer, if desired, beat butter and sugar until light and fluffy. Beat in egg. Add milk and flour mixture alternately, making three additions of flour and two of milk, beating well after each addition. blend in cinnamon, allspice, cloves, nutmeg and vanilla. Pour batter over pineapple slices.
Place dish towels over top of slow cooker (see tip). Cover and cook on HIGH for 3 hours or until a toothpick inserted in center of cake comes out clean. To serve, slice and invert on plate. Top with vanilla ice cream.
TIP: To prevent accumulated moisture from dripping on the cake batter, place two clean dish towels, each folded in half (to create a total of four layers), across the top of the cooker before covering with lid.