One dog slows down over their food. The other finishes and walks over, both go still, and a growl follows. You do not need to teach them to share a bowl. You need a mealtime where neither dog has to defend access to food.
Feed them in separate rooms with doors closed, or behind secure barriers that prevent reaching each other. Pick up bowls and leftover food before they meet again. Manage chews and food puzzles separately too. Don't stand between two tense dogs, pull a bowl away, or punish a growl. If a fight has occurred, speak with your veterinarian and a qualified, reward-based behavior professional before trying any shared setup.
Look beyond the bowl
Watch whether the tension happens around dropped crumbs, the kitchen, toys, beds, or attention from people. Keep a simple note for a professional. Sudden guarding can be influenced by pain or health changes, so veterinary checks matter. Make sure each dog can rest and access water without being blocked by the other.
A specialist may help build calmer responses at safe distances, but you can keep feeding separately long term. It is not a failure of training. Two dogs do not need to enjoy the same dining room any more than they need to want the same toy. The practical win is that both eat and leave the meal relaxed. After setting up separate feeding spaces, the second-dog household guide has more on sharing a home without making dogs share meals. Keep the food areas apart.
Sources: Dogs Trust: Resource guarding in dogs. Dogs Trust: How to understand your dog's body language.