Preheat oven to 350°.
Place one sheet of puff pastry on a piece of parchment paper and roll out until big enough to cover a 9-1/2" springform pan. Place in the pan and trim off the square edges. Stab bottom in places with a fork.
Sprinkle almond flour to cover the bottom of the puff pastry-lined pan. Arrange plum quarters over, place in oven and bake for 25-30 minutes or until puff pastry lightly browns.
While puff pastry and plums bake, whisk together in a bowl the egg, sugar and whipping cream.
Once puff pastry is done, remove from oven and pour the mixture over. Place back in oven and bake for an additional 15-20 or until mixture turns a golden yellow.
Let cool briefly. Remove tart from pan and peel back parchment paper.
Serve warm or room temperature.