4 tablespoons unsalted butter, melted, plus more for pan
2 cups all-purpose flour (spooned and leveled), plus more for pan
1 cup packed light-brown sugar
1 ½ teaspoons baking powder
½ teaspoon baking soda
1 teaspoon salt
1 large egg, lightly beaten
¾ cup whole milk
1 bag (12 ounces) cranberries
1 tablespoon turbinado sugar, for topping (optional)