It’s normal for a cat to go act as though they are burying the remains of their food after a meal. They may do this whether or not there is any food left in the bowl. The reason is that the cat is hiding his leftovers so nobody else can eat it. Wild relatives of the domestic cat, such as the Scottish Wild Cat, sometimes bury their food. However, small cats usually eat all their prey in one sitting because a bird or mouse can be consumed in a single meal. Larger cats kill much larger prey, so they more often find the need to hide the remainders of the carcass. Leopards are known to hide their food in trees to protect it from other animals. Bobcats, pumas, and cheetahs are also known to hide their leftovers, sometimes by covering it with leaves.
There is another belief about this behavior, which is that a cat tries to bury their leftover food because they think it’s poop. This is most evident when a cat eats some of their food, decides they dislike it, and starts pawing the floor. They may look at you as they do this. My neighbor’s cat Samantha does this whenever I feed her dry food. She likes the soft food that comes in foil containers, but hates the dry food from a packet. When I surrender and get out her favorite tuna flavored jelly, she immediately devours it completely. Then she paws at the ground for a bit, just in case any little crumbs remain.