Yummy Marbled Pound Cake

Ingredients

• 1 cup (2 sticks) unsalted butter, softened, plus 1 tablespoon melted butter for brushing
• 1 2/3 cups plus 1 generous tablespoon whisked cake flour (whisk, don’t sift, before measuring)
• 2 rounded tablespoons (one 0.8-ounce packet) dried buttermilk
• 1 teaspoon baking powder
• ¼ rounded teaspoon salt
• 4 ounces bittersweet chocolate, finely chopped
• 1 1/3 cups granulated sugar
• 4 extra large eggs, made tepid by submerging in a bowl of very hot tap water for 10 minutes
• 2 teaspoons pure vanilla extract
• 2 teaspoons minced lemon or orange zest (optional)
• confectioners sugar for dusting