1. Preheat oven to 350°F. Grease a 9-inch square pan.
2. In a large bowl, combine brown sugar, margarine and eggs; mix well.
3. Stir in apple sauce and vanilla; blend thoroughly. Stir in flour, cocoa, cinnamon, baking powder, baking soda and salt; mix well. Stir in nuts. Pour into prepared pan.
4. Bake for 25-35 minutes, or until a toothpick inserted in the center comes out clean. Cool on a rack; cut into squares.