Flavor does not matter, presentation does not matter but the food shouldn’t make you sick, and should ideally have enough calories per day for the average person to survive (2000 kcal min).
Edit: I am not in any danger of starving or malnutrition, nor am I insolvent. I’m mainly asking this question out of curiosity on how people would approach a solution :)
My guess would be live like an aboriginal. Your diet consists of all natural unprocessed food. You wake up with the sun every morning, hunt your prey with weapons made from sticks and sharpened rocks. You have fire so you cook the meat, and you have fresh picked fruits and veggies to boot.
Thats pretty good body nutrition and the cost per meal is only the energy that it takes to slaughter and cook the meat. And gather the fruits and veggies of course.