In small bowl, mix first 4 ingredients (Streusel topping) with a fork until crumbly and set aside.
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.
Heat oven to 350 degrees. Uncover pan and bake for 35 to 40 minutes until golden and toothpick inserted in center comes out clean.
Combine glaze ingredients and drizzle over cake once completely cooled.