Preheat over to 350°F Grease a 10-inch bundt pan well, brushing it with melted butter or nonstick cooking spray.
In a medium bowl, whisk together flour, baking powder, baking soda, nutmeg and cinnamon.
In a large bowl, using an electric mixer, cream together butter and sugar until fluffy. It will look sandy when well-combined. Beat in eggs, one at a time, followed by pear/apple sauce and vanilla extract.
Working in two or three additions, alternately add flour mixture and milk to the sugar mixture. Stir only until just combined, then gently stir in the diced pears.
Pour into prepared pan and bake for 60 minutes, or until a tester comes out clean and the cake springs back when gently pressed.
Let cake cool in pan for 15 minutes, then turn out onto a wire rack to cool.
Dust with powdered sugar before serving.