Melt 2 tablespoons butter in a 10-inch skillet over medium-low heat. Add the brown sugar and stir until the sugar begins to melt. Add the pecans and cook for 2 more minutes. Transfer the pecan mixture to a small dish and set aside. Reserve the skillet for the pancake.
In a small bowl mix together the flour, pumpkin pie spice, sugar and salt. Set aside.
Melt the remaining 3 tablespoons of butter. In a large bowl, add egg yolks, buttermilk, vanilla and melted butter and whisk until blended. Gradually whisk in flour mixture. Stir in the pumpkin puree.
Beat the egg whites until soft peaks form and gently fold into the pumpkin mixture. Gently spoon the batter into the reserved skillet. Sprinkle the top of the pancake mixture with the reserved pecan mixture. Bake for 20 to 30 minutes or until golden brown.
Dust the pancake with confectioners' sugar. Cut into wedges and serve with maple syrup.