1. Heat oven to 350ºF. Spray 15x10x1-inch pan with cooking spray. Line with parchment; spray with additional cooking spray. Sprinkle clean kitchen towel with icing sugar. Prepare cake batter as directed on package. Add dry jelly powder; mix well. Pour into prepared pan; smooth top.
2. Bake 26 to 28 min. or until top of cake springs back when touched in centre. Immediately invert cake onto towel; remove pan. Carefully peel off parchment. Starting at one short side, roll up cake and towel together. Cool completely on wire rack.
3. Unroll cake; remove towel. Spread ice cream over cake. Reroll cake; place on plate. Freeze 1 hour or until firm.
4. Frost cake with Cool Whip; sprinkle with zest. Freeze 1 hour.
Note: For best results, use kitchen shears to trim edges of parchment paper to make even with sides of pan before filling with batter and baking cake as directed.
How to Grate the Citrus Peel: Always wash and dry citrus fruit before grating. Move the whole fruit up and down on the side of the grater with the smallest holes to remove ONLY the surface of the fruit peel. (The inner white part is bitter.) Continue to grate the fruit until you have the desired amount of grated peel, rotating the fruit on the grater as necessary. Use a pastry brush or old clean toothbrush to aid in cleaning grater.