We used ½ lb (about 1 cup, halved and seeded) Korean grapes, a hybrid of Concord grapes, for this recipe: http://www.epicurious.com/recipes/food/views/concord-grape-cornmeal-cake-51122620
We also used 1% milk and white vinegar in lieu of buttermilk, following these guidelines: http://www.thekitchn.com/how-to-make-a-quick-easy-buttermilk-substitute-cooking-lessons-from-the-kitchn-185757 (Sept. 2016)
Cooking Adventures 