Kicked-Up Tuna Melts

canned albacore white tuna, packed in water (, drained)

mayonnaise ((or substitute half mayo, half plain Greek yogurt))

red onion (, finely chopped (or yellow onion))

capers (, rinsed and drained)

fresh lemon juice

coarse salt

freshly ground black pepper

dried oregano leaves

slice crusty bread

thin slices tomato

slice provolone cheese