Plum Coffee Cake

Soft sour cream cake, plum butter, sliced plums, and a brown sugar streusel, this Plum Coffee Cake is the perfect end of summer breakfast cake.

What is streusel?

Streusel is similar to the crumb topping you would find on a coffee cake but it is usually a bit thicker and slightly less crumbly. I like it a lot for a fruit coffee cake because it absorbs some of the moisture from the fruit make it a bit softer. This version uses half white sugar and half dark brown sugar to add a little extra flavor and softness.

What is the difference between a coffee cake and a buckle?

A coffee cake with the addition of fruit is really called a buckle! Which is wild to me because I only knew of a buckle as being a belt buckle but yeah, technically this recipe is a buckle and you are more than welcome to call it that.

Can I swap out the fruit?

Yes! Just make sure your fruits aren’t too juicy. I would make sure to still do a combination of jam and then a stone fruit. Like the blackberry raspberry jam from these jam and cream filled donuts with sliced peaches or fresh raspberries. Don’t use strawberries as they will release too much moisture.

Can I make this coffee cake in advance?

Yes! This cake is delicious warm from the oven (it does need to cool a bit first to hold together) but you can also make it the day before, let it come to room temp and cover the top with a sheet of plastic wrap. If you want to make it a few days in advance, transfer it to an airtight container and store it in the fridge; just be sure to let it warm up or come to room temperature before serving it.

Tips for making a Plum Coffee Cake

• Any type of plums will work for both the plum butter and the topping. My favorite combo is using Italian prune plums for the plum butter and black plums for the fresh sliced plums. Italian prune plums don’t have as much moisture so the coffee cake won’t be as juicy if you use them as the sliced plums.
• Make sure all the ingredients are at room temperature – this will help get a smooth and fluffy cake batter.
• I recommend using this 9″x9″ square pan from USA pan because it’s non-stick, and the sides are nice and tall. If you want to be able to lift the whole cake out, I recommend adding in a rectangle of brown parchment paper that reaches from one side to the other to use as a sort of sling.
• This cake can be difficult to tell when it is finished baking, but you’ll know it’s done when the streusel is golden brown and there isn’t MUCH of a wobble left on the cake. It’s ok if it still wobbles a little bit though.
• Let the cake cool for at least 15-20 minutes before slicing and serving.

Additional Coffee Cakes to try!

• Raspberry Almond Coffee Cake
• Cherry Coffee Cake
• Raspberry Apricot Coffee Cake

Ingredients for Plum Coffee Cake

• Sour Cream: Sour cream is used in the cake to make it nice and fluffy but full fat greek yogurt will work too!
• Sugar: White granulated sugar is used in the streusel and cake batter and dark brown sugar is also added into the struesel.
• Vanilla Extract: Vanilla adds flavor and enhances the sweetness of all of the elements.
• Salt: Fine sea salt helps balance out all of the sweetness in the cake and enhances the flavors.
• All Purpose Flour: Any all purpose flour will work for this cake, I use King Arthur all-purpose flour! The flour is used in both the cake batter and the struesel.
• Butter: Butter adds moisture and richness to this cake and to the streusel layer. I use salted butter but you could use unsalted too for this cake.
• Baking Soda & Baking Powder: These both help make the cake rise – make sure to check the expiration date! If they are expired, they won’t be very effective.
• Eggs: I use standard large eggs from the store, make sure they are at room temperature.
• Sour Cream: Sour Cream adds richness and moisture to the cake without making it too heavy. As mentioned in the tips, you can replace it with full fat greek yogurt or quark if needed.
• Plums: I used Italian prune plums for the plum butter and black plums for the sliced plum layer but using 100% black plums will work too!

How to make a Plum Coffee Cake?

Make the Plum Butter

• Rinse, pit, and dice the plums into 1″ chunks.
• In a large heavy bottomed pot, add in the plums and water. Cover with a lid and place over medium low heat.
• Cook for about 10 minutes until the juices are bubbling up past the chunks of plum.
• Remove the lid and continue cooking and stirring until all of the plums and their skins have broken down.
• Keep cooking and stirring until thick and the mixture no longer looks thin and watery. This usually takes about 15-20 minutes.
• Once thick, remove from the heat and set aside to cool.
• Transfer to a large shallow dish to let it cool completely while you move onto the next step. It doesn’t need to be fridge cold but it can be!

Make the Streusel

• In a medium bowl add in the soft butter, both sugars, cinnamon salt and vanilla. Use a fork to stir together until smooth.
• Pour in the flour and use the fork to rub the flour into the butter mixture until fully combined.

Cake Batter

• Preheat the oven to 350 F and place a rack in the center.
• In a medium bowl add in the sugar, flour, baking soda, baking powder, and salt and whisk to combine.
• Add in the butter, sour cream, eggs, and vanilla.
• Use the paddle attachment or an electric hand mixer to mix the ingredients first on medium low until 90% combined.
• If not using a non-stick pan, spray the metal pan with your baking spray and line with a rectangle of parchment that is 15″ x 8″ from one side to another. Pour in the cake batter.
• Smooth out the cake with a rubber spatula or a mini offset spatula.

Assemble and Bake the Cake

• Carefully spoon the cooled plum butter on top of the cake layer. Use a mini offset spatula or the back of a spoon to spread the plum butter into an even layer. Do your best not to mix it with the cake batter.
• Place the cake in the fridge or freezer while you prep the plums.
• Cut the plums in half and remove the pits. Then cut each half into four slices. Lay the slices down on their sides in rows across the top of the cake to cover the surface.
• Clump the streusel and sprinkle it over the fruit layer.
• Place the cake into the preheated oven and bake for 30 minutes. Rotate the cake 180 degrees and bake for 30 more minutes.
• The cake will be done when the streusel will be slightly more golden brown in some spots and the cake should only have a very slight or no wobble.
• Once baked, remove from the oven and leave to cool for at least 15-20 minutes on a wire rack. Run a knife along the edge between the cake and the pan. Then either lift the cake out with the parchment or slice the cake while it’s still in the pan.

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