Hi Debby! What a fun gift! We'd recommend using the paste in the cake in place of the zest called for, try 2 teaspoons to start. And then in the icing for the cake, you can try combining a tablespoon or two, depending on taste, of the lemon powder with the confectioners' sugar and using water in place of the lemon juice called for. We hope this helps and happy baking! 

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