Could I use sour cream to replace buttermilk?

Yes, you can. Sour cream is thicker than buttermilk though, so you will need to thin it out so it can provide the additional liquid needed. Since this recipe calls for 1 cup of buttermilk, use 3/4 cup of sour cream and 1/4 cup of milk. I would recommend letting it sit for 5 minutes or so after you whisk it together so the milk has a chance to sour some as well. If you don't want to use milk, you can also use water.