Preheat the oven to 375 degrees and line a baking sheet with parchment paper.
In a large bowl, combine the ground beef, crushed Ritz crackers, chopped apple, sage, onion, egg, milk, salt, and pepper.
Mix everything with clean hands until the ingredients are evenly distributed but not overworked.
Shape the mixture into a loaf about 8 inches long and place it on the prepared baking sheet.
Spread the ketchup evenly over the top of the loaf.
Bake for 45 to 50 minutes until the internal temperature reaches 160 degrees.
Remove from the oven and let the meatloaf rest for 10 minutes before slicing.