Preheat oven to 350 degrees (F).
Beat butter and cream cheese with sugar until very light and fluffy, about 5 minutes.
Add eggs, one at a time, beating until blended.
Add flour mixture in thirds, alternating with sour cream. Do not overbeat.
Add the vanilla extract and mix until just blended.
Pour batter into Bundt pan and smooth the top. Bake for 38-40 minutes. Check for doneness by testing the center with a toothpick; it should come out clean. Be careful not to overbake.
Cool in pan for 10 minutes before unmolding to cool completely on a wire rack. Let cool a little longer before slicing the cake. It is best served warm.
Whisk ingredients together until the glaze is smooth and pourable. Add a little more milk if the mixture is too stiff. Drizzle over top of cake.