Place a cup of heavy cream in a bowl. Whisk until firm peaks form.
In a bowl, combine the hot water, gelatine powder and erythritol. Stir to dissolve and let cool for 10-15 minutes and add lemon juice.
Incorporate the gelatin into the whipped cream using an electric mixer to blend the mix together. Add lemon zest and continue mixing for an additional three minutes until fully combined.
Pour the mixture into forms or glasses. Chill in the refrigerator for two to three hours to firm.