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 :)
The other dude is correct about proteins: legumes and cereals both have them, the issue is that they each have only some of the essential amino acids, while the body needs a certain proportion of them. But legumes and cereals combined have all those acids, so they supply the protein. That’s the whole idea of the legumes+cereals diet.