A. Promise him a romantic home-cooked meal.
B. Make it all vegetarian.
You can broil and stuff an avocado with polenta and chestnuts. You can handmake a rustic tart with homemade crust and use all vegetables from your garden. You can put all this on a plate with a fancy double-gold-medal-winning chardonnay and perfectly cooked green beans (also from the garden).
He will eat it. He will appreciate it. He will agree that vegetables are important and acknowledge your concern that neither of you get enough of them. He will reiterate that he likes vegetables okay. He will thank you for your trouble and tell you that you are wonderful for making him such a nice meal.
But through the whole thing, he will still be looking around for the main course.