Baking · Cake

Upside Down Rhubarb Pistachio Cake with Strawberry Custard

This upside down rhubarb pistachio cake is the kind of recipe that looks like it took far more effort than it did. The rhubarb caramelises against the sugared base of the pan and when you flip it, it reveals the most beautiful pink and green pattern underneath. The olive oil and sour cream batter is incredibly moist and tender with toasted pistachios adding nuttiness and a gentle crunch throughout. The strawberry custard is made from scratch with blended fresh strawberries and sets into something silky, bright, and deeply flavoured. Together they are a combination that tastes like early summer in the best possible way.

Recipe inspired by @by_manuela.

Ingredients

Rhubarb Base

• 300g rhubarb, cut into uniform lengths to fit the pan
• 3 tbsp white sugar
• Zest of half an orange

Cake Batter

• 166g plain flour
• 2 tbsp cornstarch
• 100g pistachio kernels, lightly toasted and finely chopped
• 2 tsp baking powder
• 1/2 tsp baking soda
• Pinch of salt
• 100g white sugar
• Zest of half an orange
• 3 medium eggs, room temperature
• 3/4 cup olive oil
• 1 cup full-fat sour cream, room temperature
• 2 tsp vanilla extract

Strawberry Custard

• 400ml whole milk
• 1 cup strawberries
• 5 egg yolks
• 50g white sugar
• 60g cornflour
• 120ml heavy cream

Method

Strawberry Custard — make this first

1. 1Blend strawberries with the milk and strain. Heat gently until just steaming.
2. 2Whisk egg yolks and sugar together until combined, then mix in the cornflour until smooth.
3. 3Slowly pour the hot strawberry milk into the egg mixture, whisking constantly, then pour everything back into the saucepan.
4. 4Cook on medium heat, stirring continuously for 2 to 3 minutes until it thickens. Let it bubble for one more minute then take off the heat.
5. 5Stir in the heavy cream and press clingfilm directly onto the surface. Refrigerate for at least 3 to 4 hours or overnight.

Cake

1. 1Preheat oven to 325°F. Bring eggs and sour cream to room temperature. Butter a 9x9 square pan and line the sides with parchment strips.
2. 2Mix white sugar and orange zest together, then sprinkle evenly over the bottom of the buttered pan.
3. 3Arrange rhubarb snugly over the sugar base in straight or diagonal rows.
4. 4Whisk together flour, cornstarch, pistachios, baking powder, and salt in a bowl. Set aside.
5. 5In a large bowl, mix sugar and orange zest together, then whisk in eggs until pale and slightly thickened, about 2 minutes by hand.
6. 6Pour in the olive oil slowly while whisking until smooth and glossy.
7. 7Add sour cream and vanilla. Whisk until fully combined with no streaks remaining.
8. 8Stir the baking soda directly into the wet mixture, then immediately fold in the dry ingredients until just combined. Do not overmix.
9. 9Pour the batter over the rhubarb and spread evenly. Bake for 30 to 40 minutes, rotating halfway through. Start checking at 30 minutes when a skewer comes out with just a few moist crumbs.
10. 10Rest for 5 to 10 minutes out of the oven. Run a knife around all four edges, place a board or plate face-down over the pan and flip in one confident motion. Serve warm or at room temperature with the strawberry custard.

Tips & Notes

Make the strawberry custard the day before so it has plenty of time to set properly in the fridge. Cut the rhubarb to uniform lengths so the rows sit neatly and look beautiful when flipped. Do not overmix the batter once the dry ingredients go in as this will make the cake tough. The flip is the most nerve-wracking part but if you rest the cake for at least 5 minutes and run the knife cleanly around all edges, it should come out cleanly. Serve the custard on the side so everyone can spoon as much as they like.