On a more practical note @BeingHappy I think lots of people who have grown up without being given any basic cooking skills can be quite genuinely overwhelmed with being asked to cook, when they probably don’t know very basic things like how to chop an onion properly, how much oil to cook it in, or how long it takes to soften in a pan. Taking a bag of shopping and turning it into a bolognese is quite daunting if you don’t know very basic prep skills.
I’d suggest you agree on a really manageable number of dishes, (three or five) that you both like, and teach him how to do those by having him help / watch you do them once then take over. My brother did this with my nieces before they went off to uni and being able to make just five dishes themselves made the world of difference.
Once he’s mastered those he can go on to more , or just cook two of those dishes a week.
To start I’d suggest:
Roast chicken, sounds daunting but actually involves no skilled prep. You just cut some carrots and onions in half and throw them in an oven dish with some new potatoes, salt pepper glug of oil and mix, then put the chicken breast r chicken thighs on top, bit of salt, pepper and oil. Heat the oven, put the dish in, set the timer and remove when done.
Pasta carbonara, cook pasta, chop and fry bacon and garlic for a few mins. Beat two eggs. Drain the pasta and put it back in the pan, put the eggs, bacon and garlic in with the pasta and cook on a low heat while stirring for three minutes till done. Grate Parmesan - done.
Pea soup, finely chop an onion. Put a small amount of oil into a soup pan, scrape in the chopped onion and cook for five minutes. Add a bag of frozen peas, water and a stock cube and cook for ten minutes. Blend and serve with toast.
Other deceptively simple options that require few skills, jacket potatoes, scrambled eggs with cheese ham or smoked salmon, tomato sauce for pasta.
Also if you teach him to make a soffritto (chopped onions, carrots and celery, softened in oil) he’ll then have the skills to be able to make bolognese, any kind of stew, chilli, most soups etc.
And yes of course you shouldn’t have to teach him to cook, he’s an adult etc etc. but at the end of the day if you want him to be able to knock out a few decent meals, and he’s willing to learn, then spending a bit of time and patience showing him a few basic skills and giving him a lot of encouragement and yummy noises will pay off.