Prune Plum Crumble Cake with Streusel
A soft almond cake layered with juicy prune plums and topped with buttery cinnamon streusel. A seasonal bake for late summer and autumn.
This prune plum crumble cake combines a soft almond cake with juicy, slightly tart prune plums and a buttery cinnamon streusel. It’s an ideal bake for late summer and early autumn, when prune plums are at their best and there’s often plenty of ripe fruit to use up.
Here in Austria, prune plums are known as Zwetschken, and they’re everywhere in late summer and early autumn. In English-speaking countries, you may also see them called Italian prune plums. They’re used here in everything from cakes to dumplings, and seeing them return to the markets and shops each year has become one of those little signs that summer is over and winter is just around the corner.
Prune Plum Crumble Cake Ingredients
Prune plums – These small, oval plums have firm flesh and a sweet-tart flavour that works particularly well for baking; they may also be sold as Italian prune plums.
Ground almonds – Add moisture and a slightly richer texture to the cake base, which helps it stay tender beneath the layer of juicy plums.
Butter – Used in both the cake and streusel, giving the base richness while helping the topping bake into crisp, irregular crumbs.
Brown sugar – Used in the streusel for a deeper flavour and slightly softer crunch than white sugar alone.
Lemon zest – Adds a little freshness to the cake without competing with the flavour of the plums.
Cinnamon – A small amount seasons the streusel and complements the prune plums without making the cake heavily spiced.
How to Make Prune Plum Crumble Cake
Prepare the tin and plums
Heat the oven to 180°C / 160°C fan / 350°F. Grease and line a 20 × 20 cm (8 × 8 inch) square brownie tin, leaving enough baking paper over the sides to lift the cake out later.
Halve the prune plums lengthways, remove the stones and toss the fruit with 1 teaspoon of flour. Small prune plums can be left in halves; quarter particularly large ones.
Make the streusel topping
Combine the flour, brown sugar, cinnamon and salt in a bowl. Rub in the cold cubed butter with your fingertips until you have a mixture of fine crumbs and larger clumps.
Keep the streusel in the fridge while you prepare the cake. Keeping the butter cold helps the larger crumbs hold their shape during baking.
Cream the butter and sugar
Beat the softened butter and caster sugar for 3–4 minutes, until lighter in colour and fluffy. Add the eggs one at a time, beating well after each addition, then mix in the vanilla and lemon zest.
Add the dry ingredients
In a separate bowl, combine the flour, ground almonds, baking powder and salt. Fold these into the butter mixture just until mostly incorporated.
Add the 60 ml milk and gently fold until you have a thick, spreadable batter. Avoid beating the mixture once the flour has been added, as this can make the finished cake firmer.
Add the prune plums
Spread the batter evenly across the prepared tin. Arrange the prune plum halves closely over the surface, cut-side up, pressing them only lightly into the batter.
The fruit should form a generous layer with relatively little exposed batter between the plums.
Add the streusel
Scatter the chilled streusel evenly over the fruit. Leave some larger pieces intact rather than breaking everything into fine crumbs, and don’t press the topping down.
Bake the cake
Bake for 50–60 minutes, checking from around 50 minutes. The streusel should be lightly browned and the plum juices should be bubbling around some of the fruit.
Insert a skewer into an exposed section of cake rather than through a plum. It should come out clean or with a few moist crumbs, but without wet batter. If the streusel is sufficiently browned before the centre is cooked, loosely cover the tin with foil for the remainder of the baking time.
Cool before slicing
Leave the cake in the tin for 20–30 minutes, then use the baking paper to lift it onto a wire rack. Allow it to cool further before cutting so the soft fruit and cake have time to set.
The cake can be served slightly warm, but it will produce cleaner slices once completely cooled.
Other Late Summer & Autumn Bakes
- Lingonberry Bakewell Tart
- Pumpkin Spice and Maple Loaf with Walnut Crumble
- Caramel Apple & Pecan Crumble Bars
- Cornelian Cherry Meringue Pie
Prune Plum Crumble Cake
Ingredients
Cake
- 150 g unsalted butter softened
- 140 g caster sugar
- 3 large eggs room temperature
- 1 tsp vanilla extract
- Finely grated zest of ½ lemon
- 200 g plain flour
- 50 g ground almonds
- 2 tsp baking powder
- ¼ tsp fine salt
- 60 ml milk
Plum Layer
- 500 g prune plums Zwetschken/Italian prune plums
- 1 tsp plain flour
Streusel
- 100 g plain flour
- 70 g cold unsalted butter cubed
- 60 g light brown sugar
- ½ tsp ground cinnamon
- Pinch of salt
Instructions
- Preheat the oven to 180°C / 160°C fan / 350°F. Grease and line a 20 × 20 cm (8 × 8 inch) square baking tin.
- Halve the prune plums lengthways, remove the stones and toss the fruit with 1 teaspoon of flour. Quarter any particularly large plums.
- To make the streusel, combine the flour, brown sugar, cinnamon and salt. Rub in the cold butter until the mixture forms fine crumbs with some larger clumps. Refrigerate while preparing the cake.
- Beat the softened butter and caster sugar for 3–4 minutes until pale and fluffy. Beat in the eggs one at a time, followed by the vanilla and lemon zest.
- Combine the flour, ground almonds, baking powder and salt in a separate bowl. Fold into the butter mixture, then fold in the milk until you have a thick, spreadable batter.
- Spread the batter evenly in the prepared tin. Arrange the prune plums closely over the surface, cut-side up, pressing them lightly into the batter.
- Scatter the chilled streusel evenly over the plums without pressing it down.
- Bake for 50–60 minutes, until the streusel is lightly browned and a skewer inserted into an exposed section of cake comes out clean or with a few moist crumbs. Loosely cover with foil if the top browns before the centre is cooked.
- Cool in the tin for 20–30 minutes, then lift the cake onto a wire rack. Allow it to cool further before slicing.
Notes
Variations and Substitutions
Change the spices: Cinnamon works well with prune plums, but you can replace it with a small amount of ground cardamom or add a pinch of ground cloves for a more pronounced autumn spice profile. Add more almond flavour: Add ½ teaspoon of almond extract to the cake batter alongside the vanilla. Keep the quantity restrained so it doesn’t overpower the fresh plums. Use other plums: Regular fresh plums can be used when prune plums aren’t available. Choose firm-ripe fruit and cut larger, juicier plums into wedges rather than halves. No ground almonds: Replace the 50 g ground almonds with an additional 50 g plain flour. The cake will be slightly less rich, so add another 1–2 tablespoons of milk if the batter is difficult to spread. Adjust the sweetness: If your prune plums are particularly tart, sprinkle 1 tablespoon of caster sugar over the fruit before adding the streusel. Very ripe, sweet plums shouldn’t need it.Storage and Freezing
Once completely cool, keep the cake covered at room temperature for up to one day or refrigerate in an airtight container for 3–4 days. Bring refrigerated slices towards room temperature before serving, or warm them briefly in a low oven. The cake can also be frozen in individual pieces for up to 3 months. Wrap the cooled pieces well, thaw overnight in the refrigerator, then warm briefly in the oven if you want to refresh the streusel topping.Zwetschken Crumble Cake FAQs
Yes, although regular round plums are often larger and juicier than prune plums. Cut them into smaller wedges and avoid using very soft, overripe fruit, which can release too much liquid into the cake.
Italian prune plums are small, elongated purple plums with firm flesh and a sweet-tart flavour. They are closely associated with the European plums known as Zwetschken in Austria and are particularly well suited to cakes and other baked desserts.
Very ripe or particularly juicy plums can release enough liquid to leave the cake directly beneath them wet. Use firm-ripe fruit, toss it with the small amount of flour in the recipe, and make sure the cake is fully baked before removing it from the oven.
Yes. The cake can be baked a day ahead and allowed to cool completely before covering it. The streusel is crispest on the day it’s baked, but the cake remains moist as the fruit settles into the sponge.
Once completely cool, keep the cake covered at room temperature for up to a day. For longer storage, refrigerate it in an airtight container for around 3–4 days and bring individual slices back towards room temperature before serving.
It’s good on its own, particularly once completely cooled, but slightly warm slices can also be served with whipped cream, vanilla ice cream or a spoonful of crème fraîche. The slightly tart plums work particularly well with something creamy rather than an additional sweet sauce.
