Taking into account bioavailability, what’s the ACTUAL healthiest meal plan?

I’ve been trying to figure out what foods give the body all the nutrients it needs, but the problem with most information provided on nutrition is that it doesn’t take into account how much the body actually absorbs! While spinach is reported to have a lot of iron, for example, not only do you only absorb about 15% of spinach’s iron content when you eat it raw, but spinach also loses most of its iron content the longer it stays out of the ground! Chocolate and meat turn out to be far better sources of iron. With that in mind, how can I figure out what to eat that will actually give me everything that the body can’t make on its own?

Taking into account bioavailability, what’s the ACTUAL healthiest meal plan?