With your hands, blend 1 stick of margarine, 1¼ cup flour and ⅓ cup of brown sugar into a dry dough. Press into the bottom of 9 × 13 ungreased pan and bake for 15 minutes.
While the bottom layer is baking, heat up the other stick of margarine along with remaining brown sugar (2 cups) in a saucepan and heat to a liquid – do not boil. Remove from fire. Temper eggs by spooning a bit of the hot mixture into the beaten eggs. This will prevent the eggs from scrambling when added to the hot caramel liquid.
Stir in beaten eggs and add the remaining 1 ¼ cups of flour, vanilla, baking powder, salt and Black Walnuts. Pour over crust and bake at 350° F (180° C) for 25 minutes.
Let stand at least an hour before cutting and serving.
Optional: Dust top of cake with confectioners’ sugar.
Recipe by Kosher Foodie Box at http://www.kosherfoodiebox.com/uncategorized/caramel-nut-cake/