Easy Kumquat Upside Down Cake Recipe

This Kumquat Upside Down Cake is like no other. Kumquats add their most unique punch of citrus flavors to a perfectly moist white cake topped with buttery caramel.

Kumquat Upside Down Cake? Yes, and it’s so good. I fell in love with kumquats last year and I’ve been looking forward to eating them again ever since. They are not easily obtained around here and they aren’t something I am going to eat all the time anyway so if you’re wondering why I said I’ve been looking forward to it since last year I wanted to give a reason. If you’re still with me, let’s talk about kumquats first, then cake!

Disclaimer: This post may contain affiliate links, which means if you decide to purchase any of the items linked in this post, I should earn a small commission. This creates no additional cost to you and helps support the work that goes into running The Fig Jar. Thank you! -Becky 

What are Kumquats?

Without getting super technical and talking about their genus and species, I’m going to just describe them as I experience them. Kumquat is a tiny citrus fruit about the size of a large grape. They have peels like other citrus fruits, sections, and seeds (that are basically the same size as seeds you’d find in an orange!). But, unlike oranges, lemons, and limes they aren’t necessary to peel since you can eat the entire fruit as-is. 

Google tells me they are in season from November to March but I’ve seen kumquat trees in my neighborhood that are full of fruit and it’s currently May. I rarely see them at grocery stores though. Only at my farmer’s market and online.

What do kumquats taste like?

I can’t really tell you what they taste like raw because all I get is an overwhelming sense of sour and I can’t discern any distinct flavor. But once they are cooked, either in cake, scones or roasted, they have a very intense citrus flavor. Orangey in a sense but not quite. They are still tart, but pleasantly so with just a touch of sweetness. And their texture becomes sticky and chewy. Kumquat marmalade (jam), or even candied kumquats (roasted kumquats coated in sugar) are especially delicious ways to enjoy these tiny fruits.

Ingredients

Kumquat Upside Down Cake

• Whole kumquats
• Salted butter
• Dry ingredients: all purpose flour, baking powder, salt, granulated sugar, brown sugar
• Wet ingredients: vanilla, egg, milk

How to make kumquat upside-down cake

So let’s talk about how to make this upside-down kumquat cake already. As I mentioned, kumquats can be very sour, but don’t fear! 

Even with the most tart kumquats, the tartness comes through in the cake but it’s the Goldilocks-just-right amount, I promise. The cake is basic, super moist, and a great way to use up a lot of kumquats. It has a butter base and comes together quickly (and it actually makes the base of this super easy berries and cream summer cake, and this fig and honey upside-down cake, too!). Let’s get to work!

Prep & Assembly

1. Slice fresh kumquats into approximately 1/4-inch slices, removing the seeds as you go. If you want uniformity in your finished cake, set aside the ends to use for roasting or discard them. It looks better to just have the slices with the fruit center on both sides. But remove the little green stem if you’re going to eat the ends!

2. Next, melt butter and mix it with brown sugar in the bottom of your cake pan. You can just mix it straight in the bottom of the pan with a fork. Then arrange kumquat slices in an even layer like so.

3. Then, whisk the flour, baking powder, and salt in a medium bowl and set aside.

4. Using an electric mixer on medium speed, beat the remaining cup of butter with sugar until fluffy for about 5 minutes. Add the egg and vanilla to the cake mixture and beat until combined.

5. Alternately add the flour mixture and milk with the hand mixer on low, beating well after each addition. Use a rubber spatula to scrape down the sides of the bowl as needed.

6. Once the batter is ready, just spread it evenly over the kumquat layer. The cake batter will be very thick. Bake for 35-45 minutes or until a toothpick inserted comes out clean.

7. After removing from the oven, immediately invert onto a plate.

Serving & Cutting This Kumquat Cake

To remove the cake from the pan, you will need to put your serving plate face-down on top of the baking dish (immediately after removing it from the oven) and quickly flip the baking dish and serving plate over simultaneously. Let me stress that you need to move fast and confidently to encourage the cake to come out clean and in one piece. 

Use dish towels to protect your fingers! It should come right out of the baking dish.

This is an absolutely gorgeous cake! But cutting it can be a little tricky if you’re trying to keep it looking pretty because the kumquats get dragged down into the cracks while cutting.

This is purely aesthetic and won’t affect the taste at all. The best knife to use is a serrated one (I LOVE this one) and slowly and gently move the knife back and forth as you cut through.

Last but not least, this cake doesn’t need any more sweetness, but it would look even more beautiful if dusted with a bit of powdered sugar!

Troubleshooting

So you followed all my instructions and flipped the cake and some of the kumquats stayed stuck in the pan? This is usually an easy fix. Just place the kumquats back on top of the cake one by one on any empty spots.

Storage Instructions for Kumquat Cake

Once it is cool, cover with plastic wrap or place cake in an airtight container and store it at room temperature for up to two days or in the fridge for up to one week.

Tried this recipe?

If you try this recipe, please leave a star rating below and let me know how it went. I’d love to hear from you!

You can also connect with me on Instagram and Pinterest.

More kumquat recipes

Kumquat Upside-Down Cake

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5 from 4 reviews

Delicious white cake topped with carmelized sweet & tart kumquats.

• Author: Becky Schmieg
• Prep Time: 30 minutes
• Cook Time: 45 minutes
• Total Time: 1 hour 15 minutes
• Yield: 8 1x
• Category: Dessert
• Cuisine: American

Ingredients

Units USM Scale 1x2x3x

• 1 cup whole kumquats (approximately)
• 1 cup plus 6 tbsp salted butter (room temperature)
• 1/2 cup brown sugar
• 1 1/2 cup all-purpose flour
• 1 1/2 tsp baking powder
• 1/2 tsp salt
• 1 cup granulated sugar
• 1 egg
• 1 tsp vanilla
• 1 cup milk

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Instructions

1. Preheat oven to 350F.
2. Slice kumquats into 1/4 inch slices, removing the seeds as you go.
   
3. Melt 6 tbsp of the butter and add it to the bottom a 10-in baking pan with the brown sugar and mix well. Arrange kumquat slices in an even layer over the mixture.
   
4. Whisk the flour, baking powder and salt in a medium bowl and set aside.
5. Using an electric mixer on medium speed, beat remaining cup of butter with sugar until fluffy, about 5 minutes. Add egg and vanilla and beat until combined.
6. Alternately add flour mixture and milk with the mixer on low, beating well after each addition. Use a rubber spatula to scrape down sides of the bowl as needed.
7. Pour the cake batter over the kumquat slices (batter will be thick) and bake for 35-45 minutes or until a toothpick inserted comes out clean.
   
8. After removing from the oven, immediately invert onto a plate.
9. Enjoy!