In a 4- or 5-qt. greased slow cooker, combine apples, cranberries, 1/2 cup brown sugar, 1 teaspoon cinnamon and vanilla.
In a large bowl, cream butter and remaining 1/2 cup brown sugar until light and fluffy. Add 1 egg at a time, beating well after each addition. Beat in pumpkin. In another bowl, whisk flour, baking powder, baking soda, salt and remaining 1 teaspoon cinnamon; beat into pumpkin mixture.
Spread over apple mixture. If desired, sprinkle with pecans. Cook, covered, on high until bubbling around edges and cake is set, about 4 hours. Serve with ice cream or whipped cream.