Combine first 6 ingredients in a large bowl; make a well in center of mixture.
Combine pumpkin, butter, and eggs, and add to dry ingredients, stirring just until moistened. Fold in chopped apple, and spoon into greased muffin pans, filling two-thirds full.
Combine 3 tablespoons sugar and 1 teaspoon pumpkin pie spice; sprinkle evenly over muffins.
Bake at 350° for 20 minutes. Remove from pans immediately, and cool on wire racks.