In a medium mixing bowl sift together the first five ingredients, set aside. Cream together the 10 ounces of butter with 2 cups of sugar in another medium mixing bowl. Lightly beat eggs and blend into creamed mixture, set aside.
In a large mixing bowl mash 8 bananas and add coarsely chopped peanuts. Alternately add sifted dry ingredients and creamed mixture to bananas and peanuts. Combine well and pour into greased 9 x 12 inch baking pan. Bake at 350 degrees for 30 minutes or until a toothpick inserted in the middle comes out clean.
In a small mixing bowl, combine 1/2 cup sugar with 1 teaspoons cinnamon. When cake comes out of oven and still warm, sprinkle sugar and cinnamon mixture on top.