Red velvet bundt cake is supposed to be moist and dense. The addition of pudding mix and oil helps to keep this cake moist, while the sour cream helps to create a denser crumb. If you've followed my recipes in the past, you know I usually use buttermilk to make moist cakes every time.  By using sour cream instead of buttermilk in this cake recipe, we're getting a more traditional dense bundt texture.