Put 7 cups flour into a large bowl.
Make a well in center of flour; put margarine in well.
Add brown sugar, baking soda, salt and 1 teaspoon pumpkin pie spice; work into margarine with fingers.
Add egg and work into margarine sugar mixture.
Gradually add buttermilk, working in flour as you go, until all buttermilk is used and a soft dough is made.
Add remaining flour, if necessary.
Divide dough into 7 equal portions.
Press one portion into a greased and floured 9 inch round cake pan.
Bake in a 350°F oven 10 to 12 minutes.
Turn layer onto a wire rack to cool.
Repeat procedure for the remaining 6 portions of dough.
Combine applesauce and remaining 1 teaspoon pumpkin pie spice.
Sweeten with granulated sugar.
Spread applesauce between slightly warm cake layers.
Do not put filling on top layer.
Cover with plastic wrap and allow cake to age for several days for best flavor.