Rhubarb cake with custard sauce

There was something about that soil-no matter how many stalks I harvested, the plants would bounce right back with new red shoots. I've cultivated a few plants here in San Francisco, but they don't thrive the same way. They haven't died yet, but I don't dare take a single stalk from them. Thankfully, when it's in season, rhubarb is easy to find at the market, so I can still make this cake and pretend it's from my own plants.

With custard sauce, it's a true dessert, but without it, this makes a lovely snacking cake that can be eaten for fika (see page 250), even while on a picnic or hike.

Makes one 9-inch (23 cm) cake.

Ingredients:

Custard sauce

• 1 cup (240 g) whole milk
• ½ cup (120 g) heavy cream
• 1 vanilla bean
• 5 egg yolks
• ¼ cup (50 g) sugar
• Pinch of kosher salt

Cake

• About 1 pound (454 g) rhubarb, ends trimmed
• 1¼ cups (160 g) all-purpose flour
• 2 teaspoons baking powder
• ½ teaspoon baking soda
• ½ teaspoon kosher salt
• ½ cup (113 g) unsalted butter, at room temperature, plus more for greasing
• 1 cup (200 g) plus 2 tablespoons sugar
• 2 eggs
• 2 teaspoons vanilla extract
• 1/3 cup (85 g) crème fraîche or sour cream

Method:

Make the custard sauce. In a small saucepan over medium-low heat, warm the milk and cream until steaming. Using a paring knife, split the vanilla bean lengthwise and use the back of the knife to scrape out the seeds. Add the pod and seeds to the warm milk mixture. Remove from the heat, cover, and set aside to steep for 15 minutes.

In a medium bowl, whisk together the egg yolks, sugar, and salt until pale yellow. Whisking constantly, slowly pour the warm milk mixture into the yolk mixture. Return the mixture to the saucepan and place over medium-low heat. Warm the sauce gently, stirring constantly, until it thickens enough to coat the back of a spoon, about 4 minutes; do not let the mixture boil or cook too rapidly or the eggs will scramble. Pour the custard sauce through a fine-mesh sieve into a jar or airtight container. Let cool, then refrigerate until ready to use.

Make the cake. Preheat the oven to 350°F (175C). Grease a 9-inch (23 cm) round springform pan with butter, then dust with flour.

Unless the rhubarb stalks are very thin, split the stalks lengthwise into ½-inch (1 cm) wide pieces. Trim the pieces into lengths that can be placed parallel to one another in the pan, so the longest stalks are in the middle and decrease in size toward the two sides. Set aside. Chop any leftover rhubarb into ¼-inch (6 mm) pieces and set aside; you should have about ½ cup (60 g)

In a small bowl, whisk together the flour, baking powder, baking soda, and salt. In a medium bowl, using an electric mixer, beat together the butter and 1 cup of the sugar on medium-high speed until light and fluffy. Add the eggs, one at a time, beating well after each addition Add the vanilla extract and beat on low speed until combined. Scrape down the sides of the bowl. Add half the flour mixture and beat on low speed just until combined, then stir in the crème fraîche. Add the remaining flour mixture and the reserved rhubarb trimmings and beat just until combined.

Scrape the batter into the prepared pan and smooth the top. Gently lay the reserved long pieces of rhubarb on top without pushing them into the batter. Sprinkle evenly with the remaining 2 tablespoons sugar.

Bake until the cake is golden brown and a toothpick inserted into the center comes out clean, 45 minutes. Transfer the cake pan to a rack and let cool in the pan for about 10 minutes. Run a knife around the sides of the cake to loosen it, release the sides of the pan, and slide the cake directly onto the rack. Let cool completely.

To serve, pour some of the custard sauce onto a plate and top with a wedge of cake.