In a medium saucepan, bring apple juice, sugar and agar-agar to a boil, reduce to medium and cook, stirring a few times, for 5 minutes, or until agar-agar flakes are completely dissolved. Keep warm.
In a food processor, purée tofu until completely smooth, about 1 minute. Add apple juice mixture, lemon juice and vanilla. Purée until fully combined and pour into prepared crust.
Cool to room temperature and refrigerate for at least 8 hours, until set. To serve, run a knife around edge of springform pan, unhinge and slice. Garnish with your topping of choice (edible flower, mint julienne, etc.). Serve chilled.