Before (and after) I went to college, I learned to cook by watching someone do it. A small notebook of home recipes written out by me while I watched someone make them went with me.
Some of my friends’ kids and my nephew have learned the same way. 4-5 easy dishes they will be happy eating, cooked with someone at home to learn first.
Teaching meal planning and different ways to cook the same thing is a different aspect, as with your mention of microwaving vegetables – eg things can be cooked according to how much time you have on hand – microwave, stovetop, oven. Making extra of something (eg a protein) to repurpose into something else later. Eggs as an easy meal.
And now there are so many good meal helpers out there. You mentioned TJs – take a look at this thread.
I think if you (or he) come up with a week of easy meals he would eat, that’s at least 2 weeks of meal rotation with leftovers.
(Many folks I know who had to cook for themselves from the get-go after never having cooked a single thing relied on 1-pot meals that they cooked once & ate for a whole week – eg beans and rice of different origins (cuban black beans, indian rajma or chana or dal, mexican pinto beans, and so on), chicken and rice, a hefty soup or stew, and so on. Would have bored me to skinniness 
but it worked great for them.)
