Kumquat Upside-Down Cake

Ingredients

• Topping
• 3 tablespoons unsalted butter
• ⅓ cup (71g) light brown sugar
• About 35 (665g) kumquats, halved
• Cake Batter
• 16 tablespoons (226g) unsalted butter, softened
• ½ cup (99g) granulated sugar
• ½ cup (106g) light brown sugar
• 2 large (113g) eggs
• 1 teaspoon pure vanilla extract
• 2 cups (240g) all-purpose flour
• 1 teaspoon ground cinnamon
• ½ teaspoon ground ginger
• 1 teaspoon baking powder
• ½ teaspoon baking soda
• ¾ teaspoon fine sea salt
• 1½ cups (360g) sour cream
• Whipped Cream (optional)
• 1 cup (235g) cold heavy cream
• ¼ cup (50g) granulated sugar
• ¾ teaspoon ground cinnamon
• ¼ teaspoon ground ginger
• ¼ teaspoon ground cloves