Using a whisk, combine the yellow cake mix, self-rising flour and ground cinnamon in a large bowl until you have a fully integrated dry mixture.
To the dry ingredients, add the beaten eggs and mashed apple pie filling. Gently stir until the batter comes together in a smooth ball. Fold in the diced apple, being careful not to overmix, until evenly distributed.
Grease two standard loaf pans with a light hand. Divide prepared batter between pans.
Using generous handfuls, evenly sprinkle the cinnamon-sugar topping over the surface of each loaf to add flavor and develop a crisp golden crust.
Put it into a preheated oven at 325°F (160°C) for 35 to 45 minutes. The loaves are finished when a toothpick inserted in the center comes out clean.
Let cool before slicing. Serve plain or with a pat of butter for a cozy finish.
