In a medium bowl, whisk the flour, baking powder, cinnamon, ground ginger, nutmeg and salt. In a large bowl, cream the remaining stick of butter. Add the granulated sugar; beat until light and fluffy. Beat in the eggs, 1 at a time. Add the vanilla. Beat in the dry ingredients in 3 additions, alternating with the milk. Spoon the batter evenly over the pears, spreading it to the edge.