If they’re underripe, they never let the stones go. When they’re too ripe, they fall apart as you twist the stone free. You can successfully substitute for other varieties of plums as I did, but the flavor won’t be quite the same. Unfortunately, they’re not as common in US grocery stores as in Europe. You’ll also find them labeled as Italian plums, Italian prune plums, or damson plums. Their color ranges from dark red or blue to purplish black. These egg-shaped plums have a rich, bittersweet flavor. Traditional German plum cake calls for Questsche plums. Since we’re exploring semantics, this recipe is technically a Pflaumenstreuselkuchen since it includes a layer of streusel on top of the plums. You’ll also see Zwetschgendatschi in Southern Germany and parts of Austria, variations of Zwetschgenplootz (Zwetschgen Plotz, Zwetschgenblootz) in Franconia, and Quetschekuche in western Germany. This means that German plum cake goes by countless names throughout all the German-speaking regions. German is a diverse language with innumerable dialects. You might know this cake by a name other than Pflaumenkuchen, but along with Zwetschgenkuchen, it’s the most common I’ve seen.
