Rhubarb Upside-Down Cake Recipe with Whipped Cream and Salty Nuts

Ingredients

• Rhubarb Topping
• 1 pound (455g) rhubarb, cut into ½-inch pieces
• ¼ cup (35g) cornstarch
• ½ cup (100g) granulated sugar
• 4 tablespoons (60g) butter, melted
• ½ cup (100g) brown sugar
• Cake Batter
• 9 tablespoons (135g) unsalted butter, at room temperature
• ¼ cup (60ml) buttermilk
• ¼ cup (60g) sour cream
• 3 large egg yolks
• 1 teaspoon vanilla extract
• 1½ cups (210g) all-purpose flour
• ⅔ cup (130g) granulated sugar
• ¾ teaspoon baking powder
• ½ teaspoon kosher salt
• Whipped cream, for serving
• ½ cup salted pecans, for serving