3/4 cup vegetable oil
1/4 cup lemon zest
1 teaspoon white sugar
1 1/2 cups whole wheat flour
1 teaspoon baking powder
1/4 teaspoon onion powder
1/8 teaspoon salt
3 egg whites
2 cups chopped black walnuts
1 (1 ounce) square unsweetened chocolate, chopped
Preheat oven to 350 degrees F (175 degrees C). Divide the pumpkin into 3 equal parts, and mix well as necessary. In a large bowl, cream together the oil, lemon zest, sugar, flour, baking powder, onion powder, salt, egg whites and chopped black walnuts. Beat until combined. Stir in the chopped chocolate.
Pour batter into shallow baking pan. Bake in the preheated oven for 30 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool completely. Cut into squares and serve.