1 1/2 cups packed light brown sugar
3/4 cup all-purpose flour
1/2 cup butter, chilled and diced
2 teaspoons ground cinnamon
1 cup chopped walnuts

3 1/4 cups all-purpose flour
1 1/2 teaspoons baking powder
3/4 teaspoon baking soda
3/4 cup butter, room temperature
1 1/2 cups white sugar
3 eggs
2 teaspoons vanilla extract
16 ounces plain low-fat yogurt
2 Granny Smith apples - peeled, cored and finely diced