Rinse the apple thoroughly under running water, remove the core and cut the flesh into even cubes. Chop the pecans with a chef's knife into coarse pieces.
Set a small skillet on the stove and heat it dry, without adding butter or oil. Toast the chopped pecans for a few minutes over medium heat until they begin to smell fragrant. Shake the pan regularly to prevent burning and let the nuts cool briefly on a plate.
Spoon the full-fat quark into a large mixing bowl. Add the apple cubes and the teaspoon of cinnamon. Stir vigorously with a spoon until the cinnamon is well incorporated into the dairy and the apple pieces are evenly distributed. Then fold the cooled pecans into the mixture.
Divide the prepared quark into a suitable bowl. Serve the dish immediately.