Mix flour, baking powder, spices, and salt in small bowl.
Using electric mixer, beat eggs and brown sugar on medium speed until thickened, about 2 minutes. Reduce speed to low and mix in flour mixture. Stir in pears, pumpkin, pecans, and vanilla by hand. Pour batter into prepared dish.
Bake cake until top is well browned, 30-35 minutes. Let cool slightly on wire rack. Serve warm, with whipped cream.