Preheat the oven to 425 degrees F. Place the snapper in a parchment paper-lined baking dish. Combine the lemon juice and zest, oil and dill in a bowl; spoon the mixture over the snapper. Sprinkle the fish with the salt and pepper. Bake for 10 to 12 minutes, or until the fish is just cooked through. Slice the buns open and spread with the mayonnaise. Place a lettuce leaf and two tomato slices on the bottom half of each bun, top with the fish and serve.