In a food processor, pulse together flour, powdered sugar, almond flour, and salt. Add butter and process until crumbly. Incorporate egg yolk and cold water until dough forms. Shape into a disk, wrap in plastic, and refrigerate for 30 minutes.

Preheat oven to 350°F (175°C). Roll out chilled dough in a tart pan, trim excess. Blind bake with weights for 20 minutes, then remove weights and bake an additional 10 minutes. Cool completely.

Heat fresh orange juice in a saucepan until steamy. Whisk eggs, sugar, and cornstarch in a bowl. Gradually combine egg mixture with warm juice, then return to saucepan and stir over low heat until thickened, about 5-7 minutes.

Remove from heat, stir in gelatin until dissolved. Cool to room temperature, then fold in butter and orange zest. Pour into crust and chill for at least 2 hours.

Whip heavy cream until soft peaks form. Sweeten with powdered sugar if desired. Keep refrigerated.

Once set, slice tart and serve with whipped cream and garnishes like berries or extra orange zest.