Sour Cream Apple Cake
["1 3/4 c. flour", "1 c. packed light brown sugar", "1 tsp. pumpkin pie spice", "1/2 c. margarine, melted", "3/4 tsp. baking powder", "3/4 tsp. baking soda", "3/4 tsp. lemon extract", "2/3 c. sour cream (can add a little more)", "2 large eggs", "1 1/2 to 2 large Granny Smith apples, peeled and sliced thin", "1/2 c. chopped walnuts (optional)"]
["Heat oven to 350\u00b0.", "Mix flour, sugar and pumpkin pie spice in an ungreased 8-inch square pan with a fork.", "Add butter and stir until mixture resembles coarse crumbs.", "Set aside 1/2 cup crumbs."]
["flour", "brown sugar", "pumpkin pie spice", "margarine", "baking powder", "baking soda", "lemon extract", "sour cream", "eggs", "apples", "walnuts"]