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This kumquat olive oil cake recipe makes a single-layer upside-down cake with candied kumquat slices baked into the top. The batter uses olive oil instead of butter, so the crumb stays soft for days.
There’s something about biting into a whole citrus slice, peel and all. Kumquats are sweet in the rind and sharp in the middle. Ten minutes in syrup tames the sharp part and leaves a little chew.
The batter is a one-bowl whisk job. Bake at 175 C / 350 F for about 40 minutes.
One timing note that actually matters: flip the cake after 15 minutes of cooling. Wait longer and the syrup sets, and the slices stay behind on the parchment.
Why You’ll Love This Recipe
- Whole kumquat slices, peel included, with no bitter pith
- Olive oil keeps the crumb moist for days
- Batter whisks together in one bowl, no mixer
- Tastes better on day two, so it’s easy to make ahead
Ingredient Notes
- kumquats: Choose firm, bright orange fruit with smooth skin. Small clementines sliced thin work if you can’t find kumquats, though they’re less tart.
- olive oil: I use a mild extra virgin oil here. A peppery, grassy oil will come through loudly in a cake this simple.
- eggs: Use room temperature eggs. They whip to a thicker, paler base in 2 minutes than cold ones do.
- whole milk: Unsweetened oat milk works as a 1:1 swap. Skim milk makes the crumb slightly drier.
- all-purpose flour: Spoon it into the measuring cup and level it, or weigh it at 190 g. Packed flour makes the cake dense.
Upside-Down Kumquat Olive Oil Cake with Candied Slices
Ingredients
Method
- Heat the oven to 175 C / 350 F. Line the bottom of a 23 cm / 9-inch round cake pan with parchment and rub the sides with 1 tsp olive oil. Slice the kumquats crosswise into 3 mm rounds and flick out the seeds with the tip of a knife.
- Stir 100 g sugar and 120 ml water together in a 20 cm / 2-quart saucepan over medium heat until the sugar dissolves. Add the kumquat slices and simmer gently for 10 minutes, until the rinds turn translucent and the syrup thickens slightly.
- Lift the slices out with a slotted spoon and arrange them in an overlapping single layer across the bottom of the pan. Spoon 1 tbsp of the syrup over them and set the rest of the syrup aside.
- Whisk the eggs, 150 g sugar and orange zest in a large bowl for 2 minutes, until pale and thick. Whisk in the olive oil in a thin stream, then the milk and vanilla.
- Sprinkle the flour, baking powder and salt over the wet mixture. Fold with a spatula until no dry streaks remain, then stop. Overmixing makes the crumb tough.
- Pour the batter over the kumquats, smooth the top and tap the pan once on the counter. Bake on the middle rack for 40 minutes, until the top is deep golden and springs back and a toothpick comes out clean. If it shows wet crumbs, bake 5 minutes more.
- Cool the cake in the pan on a rack for 15 minutes. Run a knife around the edge, invert onto a plate and peel off the parchment. Brush the reserved syrup over the warm top.
Notes
- Remove every kumquat seed before simmering, since they're hard to spot once the slices are glossy.
- Use a 23 cm / 9-inch cake pan with a solid bottom, not a springform, so the syrup can't leak.
- Invert the cake after exactly 15 minutes of cooling for clean release.
- The cake tastes best after resting a few hours or overnight.
Tips for Success
- Slice kumquats a consistent 3 mm thick so every ring turns translucent in the same 10 minutes of simmering.
- Whisk the eggs and sugar for a full 2 minutes until pale and thick, since that trapped air keeps the crumb light without a mixer.
- Pour the olive oil in a thin stream while whisking so the batter stays smooth instead of looking split.
- Invert the cake after 15 minutes in the pan, then peel the parchment off while the syrup is still tacky.
- Brush the reserved syrup on while the cake is warm so it soaks into the top instead of sitting on it.
Variations
- Add 1 tablespoon of finely chopped fresh rosemary to the batter for a savory edge that pairs well with the citrus peel.
- Replace 40 g of the flour with fine almond meal for a denser, nuttier crumb. This version is no longer nut-free.
- Bake the same batter in a 12-cup muffin tin with 2 or 3 kumquat slices per cup. Start checking at 18 minutes.
Storage and Reheating
Kumquat olive oil cake keeps covered at room temperature for up to 2 days, or in the fridge for up to 5 days. The syrup-soaked top stays moist, and the flavor deepens overnight.
To warm a slice, microwave it for 10 seconds, or heat it on a baking sheet at 150 C / 300 F for 5 minutes. Cold cake is fine too, but the olive oil crumb tastes best at room temperature.
For longer storage, freeze cooled slices wrapped in plastic and foil for up to 2 months. Thaw them overnight in the fridge.
Serving Suggestions
Serve a slice with a spoonful of plain Greek yogurt or lightly whipped mascarpone. The tang cuts through the sweet syrup.
It works at breakfast with strong coffee or as a dessert after a light dinner. A pot of Earl Grey on the side suits the citrus peel.
For a dinner party, bake it the day before and brush with a little extra warm syrup just before serving.
FAQ
Why did my kumquat olive oil cake sink in the middle?
A sunken center usually means the cake came out underbaked or the oven door opened too early. Bake the full 40 minutes before checking, and look for a top that springs back and a toothpick with no wet crumbs. If crumbs are wet, give it 5 more minutes at 175 C / 350 F.
Can I use clementines or oranges instead of kumquats?
Yes, use 2 small clementines sliced 3 mm thick, peel on and seeds removed. They’re sweeter and less tart, so cut the syrup sugar to 80 g. Simmer them 12 to 15 minutes until the peel turns translucent, since thicker rinds soften slower than kumquat skin.
Can I freeze kumquat olive oil cake with the candied slices on top?
Yes, it freezes for up to 2 months. Cool the cake completely, wrap individual slices in plastic and then foil, and thaw them overnight in the fridge. The kumquat topping stays glossy, though the syrup may look slightly wetter after thawing.
What goes well with kumquat olive oil cake?
Plain Greek yogurt or lightly whipped mascarpone balances the sweetness. A cup of Earl Grey or black coffee works too, because both stand up to the citrus peel. For dessert, drizzle any syrup left in the saucepan over the plate.
How do I make kumquat olive oil cake dairy free?
Swap the whole milk for unsweetened oat or almond milk in the same 120 ml amount. Everything else is already dairy free, since olive oil replaces the butter. Choose oat milk if you also need to keep the cake nut-free.
What’s the difference between olive oil cake and butter cake?
Olive oil cake has a looser, moister crumb because oil stays liquid at room temperature, while butter firms up as it cools. It also skips the creaming step, so you whisk eggs and sugar and fold in flour. Mild extra virgin oil adds a faint fruity note.
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