Sprinkle gelatin evenly onto the water. Let it sit for at least 5 minutes to bloom.
In a medium bowl, smoothen the cream cheese with a rubber spatula until creamy. Mix in sugar. Then add lemon juice (if using) and yogurt. Mix until the mixture becomes really smooth.
In a cold bowl, whip the cream until thick and creamy with a cold whisk. Cold equipment will speed up the whipping process.
Fold the whipped cream into cheese mixture.
Melt the bloomed gelatin in a microwave or bain-marie. Heat just until it is fully dissolved. Combine well with the cheese mixture.
Pour mixture into prepared crust base. Spread and smoothen the top with an offset spatula.
Cover and refrigerate for at least 6 hours or best overnight. The cake will set better when chilled longer. To remove the cake ring, wrap the sides with a hot wet towel until it loosens up. Then, slice and enjoy!