Can I substitute buttermilk for sour milk?

Yep, I made this twice so far and used buttermilk that is from a powder I keep in the freezer. 1/2 the cake was wolfed down within 5 minutes so I am guessing it is OK. Very moist and tender cake.

I've made it with buttermilk, too. Really great cake. In case you didn't believe everyone else. :)

I've made this recipe twice - both times with buttermilk. Came out great. (Really delicious cake, btw.)

I have made bundt cakes before using sour milk and have not had a problem with the substitution...I say go for it.

I say yes. Typically you can exchange one for the other in recipes.