If you can't find Italian prune plums, try this with another plum variety, or any other stone fruit - Look for something on the softer side that will "melt" into the batter. This recipe is so good, I honestly think it would be very difficult to fail! One other thing to point out is that as with all recipes that have stood the test of time, a few of the measurements change along the way. A quick Google search will warrant variations with 1 teaspoon cinnamon versus 1 tablespoon. I went for 1½ tablespoons and found that to be perfect - but use however much or little as you like! The same holds true for the sugar which is listed as ¾ cup in certain recipes, and 1 cup in others.