Preheat oven to 400° F.
In a small mixing bowl break up the tuna with a fork and combine the ¼ cup of mayonnaise. If adding additional ingredients, add in the celery, onion, and parsley and stir to combine. Mix until well combined and set aside.
Brush one side of all 4 Wonder® bread slices with olive oil.
Place 2 slices of bread, olive oil side down on a sheet pan
Equally, divide tuna mixture between both slices of Wonder® bread. Spread out evenly.
Top both slices of bread with a cheddar cheese slice.
Option: Also top with tomato slices and pickles.
Place the remaining 2 slices of bread, olive oil side up, on top of the sandwich.
Place in oven, until cheese is melted, about 4-6 minutes.
Remove and allow to cool slightly. Serve with cut-up veggies of your choice and enjoy!