Peach, Blueberry & Cardamom Upside-Down Cake — Three Many Cooks

Ingredients

• 3 tablespoons unsalted butter
• ½ cup brown sugar
• ½ teaspoon ground cardamom
• 1 large peach, pitted and sliced
• ½ cup blueberries, rinsed
• 1 ¼ cups all-purpose flour
• 2 tablespoons cornstarch
• 2 teaspoons baking powder
• ¼ teaspoon salt
• ½ cup milk
• 1 large egg plus 1 yolk (or two medium eggs)
• 1 teaspoon vanilla extract
• ½ cup (1 stick) unsalted butter, very soft
• 1 cup sugar