Drain the tuna well and mix it together with the mayonnaise, salt, and black pepper in a bowl. Peel the avocado, remove the seed, and cut it into thin slices.
Prepare 2 slices of bread and spread mayonnaise over one side of each. Spread the tuna mixture from Step 1 evenly over one of the slices and top it with cheese and avocado. Then put the other slice of bread on top to make a sandwich.
Place the sandwich in a frying pan over medium heat and toast it until both sides have browned. Cut it in half and it's ready to eat.
Story Behind this Recipe
This is a basic sandwich that's often served in American diners and the like. Since it's easy to make at home I don't often order it when dining out. Whenever I do feel like eating one I make it for free at home.
I used canned tuna in water this time. I also recommend using sour dough bread! You could also cook a tuna patty in olive oil and sandwich it between 2 pieces of toast, that way tastes pretty good too. Tuna melts don't normally contain avocado but I think tuna and avocado goes well so I put some in.