Ingredients 1 1/4 cups unbleached all-purpose flour 1 1/4 cups cake flour (not self-rising) 1 1/4 teaspoons baking powder 1/4 teaspoon baking soda 3/4 teaspoon kosher salt 1 stick (1/2 cup) unsalted butter, room temperature 1 cup granulated sugar 1 vanilla bean, seeds scraped Grated zest of 1 orange 2 large eggs, plus 2 large egg yolks, room temperature 1 cup buttermilk, room temperature 1 cup granulated sugar 1 tablespoon grated orange zest, plus 1/2 cup fresh orange juice 1 teaspoon grated lemon zest, plus 2 tablespoons fresh lemon juice 8 large egg yolks, room temperature 1/4 teaspoon kosher salt 10 tablespoons unsalted butter, cut into 1/2-inch pieces 2 sticks (1 cup) unsalted butter, room temperature 7 to 8 cups confectioners' sugar 1/2 cup whole milk 1 1/2 teaspoons pure vanilla extract Dried orange slices, for garnish (optional) Preparation Cupcakes: Preheat oven to 350 degrees with rack in center....