In the mixer, add the flour, brown sugar, orange zest, minced walnuts, half the butter, and beat to form a lumpy dough.
Lay the puff pastry on a buttered baking pan. Cut the apple in wedges and place them unevenly on the pastry. Sprinkle a little sugar on the apples. Add the lumpy dough in pieces all over.
Bake at 185°C for 40 min with extra heat on the top and bottom oven elements and air, on the bottom rack.
In a saucepan, add the creme fraiche, in strong heat, and bring to a boil.
In a large frying pan, heat the sugar over high heat.
Once it starts to melt, stir so as not to burn, until the sugar crystals are no longer visible.
Add the creme fraiche, stirring, over low heat, to form a homogeneous mixture.
Add the remaining butter and salt, and stir.
Take the frying pan down from the fire and place it on a cold surface to cool down.
Pour the caramel over the pie.
Place it in the fridge for at least 1 hour, to thicken.
Serve with a little whipped cream and cinnamon.