Thinly slice an onion using a mandolin or knife
Cook the sliced onions with a little salt until they are nice and brown
In a bowl, combine drained tuna, diced pickle, mayo, a touch of chili oil, salt, black pepper, and a touch of lemon juice
Slice the bread
Build the sandwich with the tuna mixture and caramelized onions
Toast the sandwich in a little bit of butter until golden
