Oatmeal Waffles with Allspiced Apple Butter

2 cups buttermilk
1/4 cup orange juice
2/3 cup quick-cooking rolled oats
1 egg
2 tablespoons packed light brown sugar
1/2 cup all-purpose flour
1/2 cup whole wheat flour
1 1/2 teaspoons baking soda
1/2 teaspoon salt
2 tablespoons melted butter, plus more for cooking
Allspiced Apple Butter, recipe follows
Whipped cream, for garnish
Fresh berries, for garnish, optional
Equipment: Waffle iron