Drain the tuna cans of their water as much as possible.
Place the tuna, green onion, cabbage, carrot, and bell pepper into a large bowl and thoroughly mix in the celery seed and soy sauce. Let sit for 10 minutes before adding the mayo and Greek yogurt.
Add the yogurt and mayonnaise and mix well. Season with salt and pepper to taste. Cover with plastic wrap and refrigerate overnight.
The next day, strain the tuna of all the accumulated water. Add more mayo/yogurt as required and serve. Enjoy!
