Preheat the oven to 350°F, and use a brush to grease a 12-cup regular-sized muffin tin with one tablespoon of melted ghee or coconut oil. (Or skip this part and just line the tin with parchment muffin liners.)
In a large bowl, mix together the tuna, scallions, and cilantro. Add the mashed sweet potato to the tuna mixture, and gently combine.
Mix in the lemon zest, jalapeño, the remaining two tablespoons of ghee or oil, eggs, and red pepper flakes. Season with salt and pepper to taste.
Mix everything together. (Using your hands is best because that way you can make sure that the fish chunks aren’t overly broken up.)
Scoop a quarter cup of the mixture into each greased muffin tin cup and flatten with the back of a spoon.
Bake the tuna cakes for 20-25 minutes or until an inserted toothpick comes out cleanly.
Transfer the cakes to a wire rack to cool. TIP: The easiest way to get them out is to put the wire rack on top of the muffin tin then flip everything upside-down, and tap them gently on the counter.
Squeeze some juice on the tuna cake before your serving.