This is a delicious, simple, 4-ingredient lunch, although it takes a little time to cook so it might be best for rest-days or short, leisurely days. And again, it requires fresh ingredients which makes the pack a little heavier. But the sweet and savory taste of this dish makes it worth it for me to tote around heavy food (it only makes you stronger anyways, right?). I think this dish is best slow-cooked in a bed of coals but can easily be done on a stove as well. I'll make this on trail when we have time for in-camp lunches, nestling my pot in our ever-present giant coal-and-ash pit and waiting about 20 minutes until the apples and onions have softened and all the flavors meld.
Half an onion, chopped
Half an apple, chopped
One packet or can of tuna
Put lots of coconut oil in a pot (a couple tablespoons - this is where you're getting most of the calories in this meal since none of the other ingredients are particularly calorie-dense) and heat it until it melts.
Add the onion and apple and sauté, stirring for about 5 minutes.
Add the tuna, and mix well.
Cover and nestle in a coal pit. Leave for about 15-20 minutes, stirring every once in a while if you can (not necessary). If you're using a stove, turn the heat down (as much as you can) and continue stirring until it is cooked to your liking.
Season with sea salt.