Preheat oven to 375°F (190° C). Lightly spray 3 (9-in./23 cm) disposable pie pans with no-stick cooking spray; set aside.
Combine oat flour, coconut flour, potato flour, baking soda and salt in medium bowl; set aside.
Mix Becel® Original margarine with sugars in large bowl. Mix in eggs and vanilla until blended. Gradually add in flour mixture; mix just until blended. Stir in rum extract and toffee bits; evenly divide into prepared pie pans.
Bake 25 minutes or until edges are golden rotating pans about halfway through. Cool completely on wire rack. Arrange doilies in center of cakes and evenly sprinkle with icing sugar. Carefully remove doilies and slice each into 16 slices.