I interpret this as a modern science question about nutritional completeness (so I don't see how adding "from a Buddhism perspective" changes the the nature of the question).
Some lay Buddhists prefer to be vegetarian, in which case I could recommend Wikipedia's Vegetarian nutrition article as an introduction to the nutritional aspects of that choice.
In summary, some of the nutrients which a naive vegetarian/vegan diet can eventually lack include protein, iron, zinc, vitamin B12, and calcium.
You may find that you must deliberately include, in your diet, substances which the average person is warned they have too much of: for example (iodized) salt, and oil.
Conventional scientific advice includes that you should have a varied diet (even if that diet is vegetarian).
IMO, beware that the diet which sustains you for a week or month or year might not be adequate to sustain you for decades. Vitamin/mineral pills might help. If your doctor knows you're vegetarian, he/she may help to monitor your health (e.g. measuring serum ferritin and whatnot occasionally).
The dietary rules for monks might be different (e.g. perhaps they eat whatever they're given).
I suppose there are other aspects of diet that are important:
- How much?
- When?
- For what purpose?
- With whom?
You presumably know that the Middle Way suggests you don't get too heavily into asceticism.
On the subject of "rice and beans" here's a recipe I use:
- cooked (optionally canned) of beans, well rinced (or iirc lentils have more iron than other beans)
- cooked rice (quantity depends on your caloric need)
- tinned sweet corn, well rinced (ditto)
- plenty of chopped raw vegetables: red or green pepper, onion, apple, celery
- oil (e.g. olive oil), lemon juice, and salt
The vegetables in this dish are robust (adding e.g. sliced cucumber would make it more perishable) so IMO you can keep it in the refrigerator for 2 days (and thus prep it once and eat it for 3 days in a row).
What you were saying about amino acids is called the "complementary protein" theory. Here is a claim about that:
While the idea that we need to combine proteins from different plant sources at every single meal has been refuted, it is still important to stress that in order to get proper nutrition one needs to eat variety of different plant foods every day, so that in each 24-hour period one gets all the essential amino acids.
