Avocado. Hands down.

We don't usually think of it as being cooked, but it can be grilled (cut sidedown on a grill for a few minutes then filled with salsa or beans, the grill make it smokey but the inside stays creamy), baked and stuffed, seared in a pan, cooked in a soup, and there are avocado fries. But it is delicious and often best uncooked, literally just completely on its own with nothing else it is rich and nutritionally substantial. It often is eaten totally on its own, or maybe with a little salt sprinkled on it but also sliced up and put on/in just about any Mexican food or put on sandwiches or in salads. Its flavor can be nutty, faintly sweet, even "grassy" and even though its delicious its subtle enough it doesn't compete to overpower whatever else its with is partly what makes it so versatile.

Obviously as guacamole it is once again highly versatile.

It works for lunch, dinner, snack, and even breakfast or dessert depending on how it's used since its fat and creaminess can stand in as butter or oil for everything from brownies to mousses to frozen desserts. It is essentially plant-made butter and was even called "poor man's butter" in places where it was common and cheap. It is ridiculously healthy largely because it is so dense with healthy fats. Those monounsaturated fats are healthy in their own right but also help the body take up nutrients from other parts of a meal, and they provide high satiety, they actually help make you feel full and sated. On top of that, avocados are loaded with micronutrients we need. I've read somewhere that if there was only one single food a person could eat and nothing else, (not that that would be a good idea, just like if you were cursed and had to choose only one) then avocado is in the front running for the best candidate because it has more stuff you need in a single place than just about any other single food. And to me at least, it would also be in the running purely for its taste.

Avocados do three great (and rare in the SAD) things, they nourish like a whole food, satisfy like a luxury ingredient, and adapts to tons of different uses/cusines as an addition or even as the primary aspect of the dish.

Oh yeah and millennial avocado toast.