Drain the tuna and chop into pieces

In a bowl mix tuna pieces, salt, pepper and celery

Top it with onion slices

Then 1 part of tuna mixture evenly (for each bread)

Place the cheese slice over it

Finally cover with other slice (out of the remaining 4)

Apply butter on the top of the slice

Grill the sandwich in sandwich griller till golden brown

Serve with tomato sauce and wafers