Place the pitted dates and walnuts into a food processor and process until a moist, sticky crumb forms that holds together when pressed

Line the base and sides of a springform pan with baking paper and secure the ring in place

Press the date walnut mixture firmly and evenly into the base of the pan and refrigerate while preparing the filling

Combine the agar agar powder and cold water in a small saucepan and allow it to hydrate briefly

Heat the agar mixture gently while whisking until fully dissolved and smooth, then remove from heat

Beat the softened cream cheese until smooth, then mix in the sweetener until fluffy

Gently mix the crushed pineapple and reserved pineapple juice into the cream cheese mixture

Slowly pour the warm agar agar mixture into the filling while mixing continuously

Whip the cold heavy cream until soft peaks form

Fold the whipped cream gently into the pineapple filling until smooth and airy

Pour the filling over the chilled crust and smooth the top evenly

Tap the pan lightly to release air bubbles, then cover and refrigerate until fully set

Remove the tart from the pan, slice, and serve chilled