I added both tuna in oil and tuna in water. I made 6 large melts and used 4 cans of tuna. You can adjust this depending on how many you want to make.
I like to mix the tuna together with the celery and onions with my fingers to get it to a uniform consistency.
Add just enough mayonnaise to hold it together. I used about 1/3 cup. Add 1 tsp. of salt and 1 tsp. of pepper.
I used Russian corn rye as my base. Mound several scoops of tuna salad on each piece of bread.
It was pointed out in the comments and I think I should add this info:
I always add the tuna salad when it is very cold so that even after the cheese is melted, the tuna is still cold. Hot tuna is not something I like very much!
Top with some pickle slices. These are my new favorites and I am a pickle connoisseur! They are organic sandwich slices from Trader Joe's.
Before I made the salad, I sliced some tomatoes and sprinkled them with sea salt. I sat them on paper towels to let some of their juices drain. Then I placed them on top of the pickles.
I topped each melt with a couple slices of Lorraine Swiss and sprinkled them with celery salt. (Note to no knead bread bakers: Put some cheese on a slice of no knead bread, sprinkle it with celery salt and broil...major yum!)