Overnight Apple Coffee Cake

Ingredients

• 1/2 cup unbleached all-purpose flour
• 1/2 cup white whole wheat flour
• 1/2 cup quick-cooking oats
• 2 tablespoons flax seed meal
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 2 teaspoons cinnamon
• 1/2 teaspoon salt
• 1/2 cup granulated sugar
• 1/2 cup brown sugar, packed
• 1/3 cup canola oil
• 1 egg
• 3/4 cup buttermilk
• 2 cups apples, peeled, cored, and chopped
• 1/2 cup walnuts, chopped (or pecans)