Drain the liquid from the tuna cans. If the tuna is packed in water, reserve a tablespoon of the tuna water and also add a teaspoon of olive oil to the tuna mixture in the next step. If your tuna is soggy and not dry, do not add water.
In a medium bowl, mix together the tuna, mustard, bread crumbs, lemon zest, lemon juice, water, parsley, onions, and hot sauce. Add salt and pepper and taste for seasoning before adding in the egg. Add egg to mixture and combine.
Line a baking sheet or a tray with parchment or waxed paper. To make a patty, shape some of the mixture into a ball and then flatten between your hands. Place all the patties on the prepared tray and refrigerate for an hour so they don’t fall apart when you cook them. If you’re in a hurry, you can stick them in the freezer for 15 minutes.
Heat the oil and butter or ghee in a large skillet over medium heat. Use less fat if you use a smaller skillet. You want the oil and butter to be warm enough so that the patties sizzle when they hit the pan, but you don’t want them to be smoking. Gently transfer the tuna patties to the pan and sauté until browned, about 3-4 minutes on each side.