In a medium frying pan, heat olive oil over medium heat. Add onions and sauté until translucent and slightly browned, about seven minutes.

In a bowl, mix the sautéed onions, tuna, panko, eggs, mayonnaise, parsley, garlic powder, onion powder, salt, and pepper. Form six large patties and place them on a plate.

In a large frying pan, heat avocado oil over medium heat. Cook patties for three to four minutes per side, or until golden.

Toast the buns in the frying pan until golden.

In a bowl, mash the avocados and season with salt to taste.

Spread a little mayonnaise on both halves of each bun. Layer lettuce, tuna burger, guacamole, and fried onions. Cover with the top halves of the buns and serve.