In a mixing bowl, combine dry ingredients. Beat in eggs, oil and vanilla. (Batter will be heavy.) Fold in pineapple, mashed bananas and nuts. Pour into a well-greased 10-inch tube pan. Bake at 350° for 60 to 65 minutes, or until cake tests done. Cool in pan 15 minutes before removing to a wire rack. When completely cooled, sprinkle with confectioners' sugar. Yield: 16 servings.