According to Pam Johnson Bennett:
In the wild, a cat may attempt to bury or cover any uneaten food in
order to avoid attracting any predators to the area. It also is an
attempt to not alert any other potential prey that a feline hunter is
in the vicinity. Cats aren’t scavengers so they don’t bury the food to
consume later – it’s strictly for protection purposes. Even an indoor
cat who has never set foot outside retains this survival instinct;
it’s just a matter of how much it concerns them and that determines to
what degree the behavior is displayed.
In my experience, burying food behaviors have been displayed in cats who are also distressed by litter box cleanliness (one cat even would rebury the other cats' poo if it wasn't covered well enough for his tastes) and other anxiety-related behaviors.
If it becomes a problem, you can pick up the bowl(s) after the cat(s) have finished their meal (always leave clean water available). A cat with a range of anxiety related behaviors can also be helped with medication by seeing your vet, but if food burying is the only behavior he is displaying I wouldn't worry about it.