In a large bowl, beat 1 cup sugar and 1/2 cup butter with a mixer. Beat in 1 cup eggnog, sour cream, rum extract and eggs until well blended. Stir in 2 1/2 cups flour, the baking powder, baking soda and salt. Spread in pan and sprinkle Streusel Topping over the batter. Cover and refrigerate at least 8 hours. I prepare it the night before.