- Line a 13 x 23-cm (5 x 9-inch) loaf pan with plastic wrap.
- In a small saucepan, bring the water, sugar and lemon zest to a boil. Simmer without stirring until a candy thermometer reads 112°C (234°F).
- In a bowl, beat the egg whites and cream of tartar with an electric mixer. When soft peaks begin to form, add the hot syrup in a thin stream while still beating. Continue beating until stiff peaks form, 4 to 5 minutes. Cover and refrigerate for 30 minutes.
- In a bowl, whip the cream. With a spatula, fold in the chilled meringue and the lemon juice.
- Spread the mixture in the loaf pan. Cover and freeze for at least 3 hours.
- Unmould and slice. Garnish with seasonal fruit and serve with a tuile or other delicate cookie.