In a food processor, combine flour, powdered sugar, almond flour, salt, and orange zest. Add butter and pulse until coarse crumbs form, about 10 seconds. Add egg yolk and water, mixing until just combined. Shape into a disk, wrap, and refrigerate for at least 15 minutes.

Roll out the dough to fit a 9-inch tart pan. Place in the pan, refrigerate for 20 minutes. Preheat oven to 200°C (390°F). Line with foil, fill with weights, and bake for 12-15 minutes. Remove weights, trim edges, and bake for an additional 10-12 minutes until golden. Allow to cool completely.

In a saucepan, heat orange juice over medium heat until steaming. Whisk together eggs, superfine sugar, and cornstarch until smooth. Gradually pour in hot juice to temper, whisking continuously. Cook mixture over low heat for 5-7 minutes until thickened. Stir in gelatin if using and mix in butter and zest until smooth.

Pour the warm orange curd into the cooled tart shell, spreading evenly. Cool to room temperature, then cover and refrigerate for at least 3 hours, or overnight.

Whip cream with powdered sugar using a mixer on medium-high speed until soft peaks form. Layer over the chilled tart just before serving.