Combine the ingredients for topping and set aside.
Sift the flour, baking powder, baking soda, and salt together; set aside.
Cream butter with extract; gradually add the sugar, beating until fluffy.
Add the eggs, one at a time, beating thoroughly after each addition.
Blend in the apple butter and cereal.
Beating only until smooth after each addition, alternately add dry ingredients in fourths and sour cream in thirds to creamed mixture.
Turn half the batter into a greased (bottom only) 13x9x2-inch baking pan.
Spread evenly to edges.
Sprinkle half of the topping mixture over batter in pan.
Spoon remaining batter into pan and spread evenly.
Sprinkle with remaining topping.
Bake at 350°F about 30 minutes, or until cake tests done.
Cool cake completely in pan.
Cut into squares and serve warm or cold.
Top with whipped cream, if desired.