Gluten-free Pistachio Cake with Blackberry Sauce

I had pistachios left over from these amazing dessert bars. There also happened to be a recent sale on blackberries at the local organic deli. So, while at the deli, I looked up desserts that used both pistachios and blackberries and found this winner. I quickly bought the ingredients I was missing and promptly went home to start baking.

 

Aren't those the best kind of days?

 

Processing the pistachios to make the "flour" was fun and I always find separating eggs rather calming. (Which is slightly weird, I know.) While the process to make this batter is a little time consuming, I enjoyed it a lot.

 

The cake was pretty with a slight hint of green when it came out of the oven.

Adding the blackberry sauce made this cake even prettier!

Don't you agree?

This cake ended up being gluten free since the pistachios acted as the flour. With the mixture of powdered and white sugar this cake ended up being very light, almost like an angel food cake or like a cake version of a macron. If you are like me and happen to have some pistachios on hand, this recipe is a good use for them.

Pistachio Cake with Blackberry Sauce (adapted from SugarHero which adapted it from Simply Recipes)

For the Pistachio Cake:
1 1/2 cups shelled pistachios, either roasted or raw
2 tbsp powdered sugar
1 tsp baking powder
4 eggs at room temperature, separated into yolks and whites
zest from one orange
1/2 cup granulated sugar, divided use
1/4 tsp cream of tartar

For the Blackberry Sauce:12 oz fresh blackberries
3 tbsp granulated sugar (or more, to taste)
1/4 cup orange juice
1 tbsp corn starch

To Make the Pistachio Cake: Preheat the oven to 350 F. Spray the bottom and sides of a 9-inch springform pan with nonstick cooking spray. Set aside.

Place the shelled pistachios in the bowl of a food processor and process for about 10 seconds, until they’re in small pieces. Add the powdered sugar and continue to process in 10-second intervals until the pistachios are a fine powder. Stop and scrape the corners of the bowl occasionally if you see pistachios are starting to build up there. The goal is to get the nuts as finely ground as possible. Don’t over-process them or you’ll risk them becoming greasy and turning into pistachio butter.
Once the nuts are finely ground, transfer them to a small bowl, add the baking powder, and whisk everything together.

In a large bowl, combine the egg yolks, orange zest, and 1/4 cup granulated sugar, and whisk well. Add the pistachio mixture and stir with a rubber spatula. The mixture will be very thick and sticky.

Place the egg whites in the bowl of a large stand mixer, and whip them on medium speed with the whisk attachment until they become foamy. Add the cream of tartar and continue to whip the egg whites, gradually increasing the speed until you reach medium-high. When soft peaks form, start adding the remaining 1/4 cup of granulated sugar, a tablespoon at a time, until it’s all incorporated. Whip until the egg whites form firm peaks but are not crumbly—they should be glossy and have body, like shaving cream.

Add a quarter of the egg whites to the pistachio mixture which will be a sticky and stiff process at first. Once it’s incorporated, your batter should be looser, so add another quarter and fold it in gently, then add the remaining egg whites in two batches, folding gently so as not to deflate the whites.
Scrape the batter into the prepared pan. Bake the cake at 350 F for 20-25 minutes, until it is puffed, golden, and the sides are pulling away from the pan. A toothpick inserted into the center should come out clean. Cool the cake on a wire rack, then release it from the springform pan to serve.

To Make the Blackberry Sauce: In a medium saucepan over medium heat, stir together the blackberries and the sugar. As the berries heat up, they will soften and release their juices. Cook the berries, stirring occasionally until they start to lose their shape. You don’t want them completely liquefied, but they should break down a little bit and be very, very juicy.

Meanwhile, whisk together the orange juice and corn starch in a small bowl until the starch dissolves. Once the berries have broken down, whisk the starch mixture into the berries and cook it for a few minutes until it starts to thicken. (It won’t be a drastic change.) Remove the pan from the heat and cool the sauce until it is room temperature. As the sauce cools, it will continue to get thicker. Store extra blackberry sauce in an airtight container in the refrigerator for up to a week.

Bake well and prosper!