Preheat the oven to 400 degrees F. Lightly coat a baking sheet with cooking spray.
In a large mixing bowl, lightly mash the avocado. Add the tuna, bread crumbs, red onion, cilantro, lime juice, hot sauce, garlic powder, salt, and egg. Mix until the ingredients are fairly well combined. (It's ok if the mixture is a little clumpy.)
Form into 6 patties, then arrange the patties on the prepared baking sheet. Bake for 10 minutes, flip, then continue baking until the outsides are lightly crisp and the cakes are cooked through, about 10 additional minutes. Enjoy warm.