My daughter asked for a dish with little gluten in it and there were five of us to feed (one a toddler). I actually made this with a couple of fresh salmon fillets as that is what I had, put it would work with a tin of tuna. I served it with broccoli and carrots and there was a bit of cheese sauce left and so I thinned it down with milk and served it in a gravy boat.
5 medium potatoes
A can of tuna (or canned salmon or fresh salmon)
Vegetables eg peas, cooked broccoli, spinach, leeks or what ever you have in the fridge or freezer (I used leeks and spinach)