Lemon Rosemary Olive Oil Cake with Blackberry Curd & Mascarpone Frosting

Over the past year, people have occasionally messaged me on Instagram asking if I sell my baked goods. I usually laugh and reply, “I’m just a home baker.” Recently, though, someone asked if I could make treats for a specific event—a baby shower on a set date—and the request felt real and definite. The person’s taste in desserts matched what I enjoy baking, so I said yes. That led to my first baking commission: two cakes.

The first cake I proposed was a lemon rosemary olive oil cake, even though I hadn’t made that specific combination before or prepared a final recipe. The requestor mentioned she liked olive oil cakes and shared inspiration photos, including a semi-naked layer cake topped with rosemary, blackberries, and figs. I’d also been experimenting with blackberry curd. The ideas came together and I typed, “How about a lemon rosemary olive oil cake with blackberry curd and mascarpone buttercream?” She loved the idea, so I got to work.

After some research, I adapted a lemon olive oil cake recipe. The original recipe yielded a 6-inch, three-layer cake, but I was aiming to serve about 20 guests, so I doubled the ingredients and baked an 8-inch, three-layer cake. The result was quite large—if your refrigerator space or arm strength is limited, you may prefer the smaller 6-inch version and halve the quantities below.

Even though I had tasted all the elements during testing, I was nervous about whether guests would enjoy the final cake. Baking on commission for the first time and serving people I’d never met added pressure. Rosemary and olive oil give the cake distinct, savory-leaning notes that may not appeal to everyone. I was thrilled to hear that many guests loved it—hopefully you will, too.

A few practical notes:

Use a high-quality, fruity extra virgin olive oil and taste it first. The olive oil flavor is prominent, and you want it to complement the lemon and rosemary rather than overpower them.
The blackberry curd amount here fills a three-layer, 8-inch cake exactly. If you make a 6-inch version, consider making the full batch of curd anyway—it’s excellent on its own or for other uses.
For the frosting I provide a range for powdered sugar because sweetness preferences vary. I prefer a lightly sweetened finish so the cake remains balanced; increase the sugar toward the higher end if you want a sweeter buttercream.

5 from 1 vote

Lemon Rosemary Olive Oil Cake with Blackberry Curd and Mascarpone Buttercream

A subtly herbal layer cake filled with sweet-tart blackberry curd and finished with a lightly sweet mascarpone buttercream, frosted in a semi-naked style. The lemon-rosemary olive oil cake is adapted from a classic olive oil cake method; the blackberry curd and mascarpone frosting balance the olive oil’s fruitiness and the herbaceous rosemary.

Ingredients

For the lemon rosemary olive oil cake layers:

4 large eggs at room temperature
400 g granulated sugar
500 g all-purpose flour
2 tsp baking powder
2 tsp baking soda
1.5 tsp table salt or fine sea salt
3 medium lemons zested and juiced
1.5 tbsp finely chopped fresh rosemary
1 1/3 to 1 1/2 cups whole milk (adjust to reach 2 cups with lemon juice)
1 1/3 cup extra virgin olive oil

For the blackberry curd:

170 g fresh blackberries
1 large egg
2 large egg yolks
75 g unsalted butter at room temperature, cut into pats
100 g granulated sugar
1 tbsp cornstarch
juice of half a lemon

For the mascarpone buttercream:

6 oz. unsalted butter at room temperature
12 oz. mascarpone cheese at room temperature
250-300 g powdered sugar (adjust to taste)
zest of half a lemon
1 tsp lemon juice

To decorate:

fresh blackberries and rosemary sprigs

Instructions

Make the blackberry curd:

Rinse the blackberries, place them in a microwave-safe bowl, and microwave on high for 1 minute. Mash with a fork to release juices, then press the mash through a sieve to yield 1/2 cup blackberry juice.
Measure the cornstarch and lemon juice and keep them ready to combine quickly when needed.
In a small heavy-bottomed saucepan, whisk together the egg, yolks, sugar, and blackberry juice. Place over low heat, add the butter, and whisk constantly until the mixture is steaming and begins to thicken (about 160–170°F), roughly 6–12 minutes.
Whisk the cornstarch and lemon juice into a slurry and add it to the curd. Continue whisking until the curd thickens significantly (about 185°F). Remove from heat and whisk for another minute or two to stop the cooking.
Transfer the curd to a clean container, press plastic wrap directly onto its surface, cool to room temperature, then refrigerate for at least 6 hours or overnight.

Make the cake layers:

Preheat the oven to 350°F and position a rack in the center.
Grease three 8-inch cake pans, line them with parchment on the bottoms and sides, and grease the parchment.
Whisk together the flour, baking powder, baking soda, and salt; set aside.
Zest and juice the lemons. You should have about 1/2–2/3 cup lemon juice; combine the juice with enough milk to total 2 cups of liquid.
In a bowl or the measuring jug, whisk together the milk-lemon mixture, lemon zest, chopped rosemary, and olive oil; set aside.
Using a stand mixer with a whisk attachment, beat the eggs and sugar on medium speed for about two minutes until light and thick.
Add one-third of the flour mixture to the eggs and sugar, mixing until just combined. Add half the olive oil mixture, mix until just combined, scrape the bowl, then repeat. Finish with the last third of the flour. Stop the mixer while the final addition is almost incorporated and fold the remainder in with a spatula.
Divide the batter evenly among the three pans (about 605 g per pan).
Bake 33–37 minutes, or until a skewer inserted in the centers comes out clean. Start checking at 30 minutes if your oven runs hot.
Cool the cakes in their pans for 10–20 minutes, then turn them out onto a wire rack to cool completely. Level the tops with a serrated knife when cool.
You can assemble and frost immediately or freeze the layers. To freeze, double-wrap each layer in plastic wrap, place in a freezer bag, and store flat on a baking sheet for up to 2–3 weeks.

Make the frosting:

Beat the butter and mascarpone until light and fluffy. Add powdered sugar gradually to reach your preferred sweetness, then blend in the lemon juice and lemon zest.

Assemble the cake:

Place one cake layer cut side up on your cake board. Pipe a ring of frosting around the edge and fill the center with half the blackberry curd.
Set the second layer cut side down on top. Pipe another frosting ring and fill with the remaining curd.
Top with the final layer, cut side down. Generously frost the top and smooth the sides with a bench scraper or offset spatula. For a semi-naked finish, leave some cake visible; you’ll likely have extra frosting.
Decorate with fresh blackberries and rosemary sprigs.

Recipe Notes

The original olive oil cake recipe includes a helpful video that demonstrates leveling cake layers and achieving a semi-naked finish—useful if you’re new to those techniques.
Freezing cake layers before frosting makes them firmer and less likely to crumble while you ice. It also helps the room-temperature frosting set on contact, so you won’t need to chill the assembled cake as long to stabilize it.
The rosemary note is present but subtle; increase to 2 tablespoons if you prefer a stronger herb flavor.