Preheat oven to 350° F and grease bottom of 9 x 9 pan with nonstick cooking spray.
In a large bowl, cream together butter and sugar. Beat in eggnog, sour cream, rum extract, and eggs until well blended.
Add flour, baking powder, baking soda, and salt and mix until just combined. Spread into bottom of pan.
In a small bowl, mix all streusel topping ingredients together with fork until crumbly. Sprinkle crumb topping over cake batter.
Bake at 350° F for 35-40 minutes or until toothpick inserted in center comes out clean. Cool completely.
While cake is cooling, whisk together powdered sugar and eggnog for the glaze. After cake is cool, drizzle over top of cake and top with extra powdered sugar.