Chestnut flour pastry:
In a bowl, combine the flours with the sugar
Add the cubed butter. Using a pastry blender, two knives, or your fingers, incorporate the butter into the flour until the mixture forms pea-sized lumps
Add the sour cream.
Using two forks, work the dough until it is homogeneous.
Wrap it in plastic wrap and refrigerate for 30 minutes.

Preheat the oven to 400°F (200°C).
Butter and flour 2 fluted tart pans with a diameter of 8″ (20cm).
On a floured work surface, roll out the dough to a thickness of 1/8″ (0.3cm).
Line the tart pans with the dough, prick the bottom with a fork, and reserve for 15 minutes in the freezer.

Pre-bake the tart crusts for 15 minutes.
Reduce the oven temperature to 350°F (180°C).

Filling:
While the tart crusts are pre-baking, melt a little butter in a pan and brown the apple quarters on all sides.
Sprinkle with sugar and moisten with lemon juice.
Cook until the sugar caramelizes.
Remove from heat and let cool.

Divide the chestnut cream among each tart crust.
Arrange the apple quarters aesthetically on the chestnut cream, reserving the lemon caramel in the pan.

In a bowl, beat the eggs with the sour cream and lemon caramel, and divide the mixture among each tart.
Bake for 35 minutes and enjoy without moderation.