Preheat the oven to 350 degrees.
Line a 15x10 pan with foil. Spray with nonstick spray and set aside.
Beat the butter and sugars until creamy. Add the eggs and beat again.
Stir together the salt, baking powder, and flour and add to the butter mixture until a soft dough forms.
Spread the dough into the pan.
Spoon the apple butter over the top and spread out evenly leaving a 1 inch border all around.
Stir together the topping ingredients until it resembles sand. Sprinkle over the apple butter layer.
Bake for 22-24 minutes. Remove and cool. Cut into 30 bars.
Stir together the powdered sugar and water.
Drizzle over the cake squares. Let set. Store in a covered container on the counter.