Does the picky eater like cheese or bacon? Sometimes either one or the other is a big hit with them. Try to add vegetables into spaghetti sauce via pureed in small amounts if that's a problem. How old is this picky eater?
What about biscuit pizza, it's my go to food for everyone. You just cook the biscuits like normal, cut them in half add sauce, cheese, and whatever else you want and bam there you have a personal sized pizza..