Using a colander, drain the canned tuna and transfer the canned tuna to a bowl.
To the bowl now add the mayo and freshly cracked pepper. Give a mix and it's ready. (see notes below for other variations you can add)
Toast the bread slices for 1 minute. Then layer the tuna mixture in one slice of bread.
Spread a little mayo on the second slice of bread and press it on the other bread to make the sandwich.
I sliced off a tiny amount of the sides and then for his lunch box, I sliced the sandwich into 4 parts.
The sides that went in are cherry tomatoes, couple cookies and assorted nuts.
Notes
A few other things that you can add to make it extra tasty:
Finely chopped red onion, or chopped pickled onion. Sweet relish is also a great choice to mix with Tuna. I skipped both these while packing the lunch box. To make it for grown up kid's lunch box or adult's lunch box, I would layer lettuce or some kind of greens, slices of tomato, few slices of avocado along with the tuna.