Lightly oil 8 or 9 eight ounce ramequins and keep them refrigerated until ready to use.
Pour the water into a small bowl and sprinkle the gelatin over it. Let stand for about 10 minutes.
Place the bowl in a larger bowl filled with hot water and stir until the gelatin has dissolved and the liquid is clear.
Process 3/4 cup of the sugar with the lemon zest in a food processor until the zest is finely ground.
Beat the egg yolks, the sugar/lemon zest mixture, lemon juice, and the salt in an electric mixer on medium speed in a large, deep heat-proof bowl until combined well.
Set the bowl over a saucepan filled with simmering water and continue beating for fifteen minutes or until the mixture is very thick and pale.
Remove the bowl from the heat.
Add the gelatin mixture and continue to beat until it has cooled down to room temperature (you can set the bowl over ice so that it cools faster).
Beat the egg whites until just foamy. On medium-high speed, add the remaining 1/2 cup sugar, one tablespoon at a time, beating well after each addition, and continue to beat until the egg whites form stiff peaks.
Beat the heavy cream with an electric mixer until stiff peaks form.
Keep on whisking the lemon/egg yolk/gelatin mixture over the ice water until it begins to thicken and set.
Gently fold in the whipped cream and then fold in the egg whites.
Pour into the ramequins and smooth the top. Refrigerate for at least 3 hours before serving. Will keep well in the refrigerator.