Preheat the oven to 375 degrees F. Lightly coat 13x9x2-inch baking pan with cooking spray or grease with shortening. In a large mixing bowl stir together the 2-1/4 cups flour, 1/2 cup brown sugar, the baking powder, cinnamon, and salt.
In a medium bowl combine eggs, applesauce, and oil. Stir in 1/2 cup nuts.
Stir apple mixture into flour mixture until well blended. Pour into prepared pan.
For streusel topping, in a small mixing bowl combine the 1/2 cup flour and 1/4 cup brown sugar. Cut in butter. Stir in the remaining 1/2 cup nuts. Sprinkle over batter.
Bake in a 375 degree F oven about 25 minutes or until a wooden toothpick inserted near center comes out clean. Cool on a wire rack. Cut into rectangles. Makes 24 to 36 bars.