Oblige him and serve him rare, unseasoned and boiled steak. Show him how much of "steak’'s flavor is just herbs and spices (plants).
I literally made him things such as buddha bowl, vegan lasagna, stuff bell peppers, sweet potato and chickpea wraps, vegan pad thai, zucchini noodles with pesto, etc. he’s acting like I feed him grass.
You’re feeding him the food his food eats. He wants his food.
Your palate needs to adjust to be able to taste healthy food again, in my experience.
If you are eating a lot of fried and processed food you don’t notice the subtle flavors of vegetables and other healthy food at first.
While a boiled steak would certainly taste terrible, as a strictly salt, pepper, ripping hot cast iron, steak enjoyer, steak tastes just fine by itself. Well by itself with the Maillard reaction.
