Ooh, that can be tricky to share your food when you're eating restricted foods or not much of it!
Thanks to one of my diets (mostly just eating clean) I got my daughter eating all sorts of roasted vegetables. I had to sprinkle cinnamon on everything though for her to eat it but she was my roasted veggie buddy!
The advice I always got, about getting through picky phases, was to keep putting variety in front of them. Even if they don't touch it. Keep it in front of them. Maybe they get desert if they at least try something besides the quesadilla. That was always hard for us though because there was so much wasted food.
One of my friends had to make soup out of everything. Her daughter would eat anything in a blended soup form.
Break out your food processor and start making purees as special sauces to sneak into his quesadilla. I used to do that when my son would only eat pancakes. At the time I was making my own baby food for my daughter so each batch of pancake batter had a different kind of baby food in it. He still has no idea.
One of my favorite tricks is... shapes! I have a little food cutter made for kids from funbites
& sandwich cutters from Fred
(mustache & lego shapes are their fav). Mine love finger food and playing with their food. When new things are smaller... they aren't so overwhelming too.