In a saucepan, mix dry ingredients gradually. Stir in pumpkin and milk. Cook and stir until thickens. Bring to a boil and cook for 2 minutes longer. Stir a small amount in the beaten eggs and then add to hot mixture. Cook 2 minutes longer and cool to room temperature. Pour into cooled, baked pie crust. For the meringue, beat the egg whites with the vanilla and cream of tartar until soft peaks form. Gradually add 6 tablespoons of sugar and beat until sugar dissolves. Spread over filling and bake at 350 degrees for 10-15 minutes.