I have been vegetarian for decades at this point, and i often cook for my omni friends and family.
A few dishes that are crowd pleasers and will not sound too intimidating/out there
- potato/leek soup
- +1 for the SK mushroom bourginion
- vegetarian lasagna
- shashuksa
- stuffed squash or zucchini etc (think rice/lentils/nuts stuffing)
- african sweet potato peanut stew
- sesame / peanut butter noodles
- enchiladas with beans/rice/veggies
- socca with various toppings
Bittman’s how to cook vegetarian is a great resource, and very helpful that it has a section in many different places that show examples of how to take a dish and make it a meal with suggestions of what to add.
A subscription to vegetarian times magazine might be appreciated, they feature easy to follow well tested recipes that appeal to a wide audience.
In recent years i turn to websites more often than books for new recipes mostly so i can access the recipe when shopping if i like it i keep it bookmarked in my browser recipes folder.
101 cookbooks is a great one, she has hundreds of recipes posted there and has written several cookbooks as well
Food 52 has some great recipes too, i make their famous one pot kale and quinoa regularly and swap around different seeds/nuts and cheese (or faux cheese)
Martha Stewart ‘s team also has a huge website of vegetarian recipes that are generally well tested and written and easy to follow
https://www.marthastewart.com/search/results?keys=Vegetarian%20
Initially they may also appreciate signing up for hello fresh or blue apron to feel a little less overwhelmed until they have a better idea of what they need to be shopping for and making. Vegetarian cooking can be very different initially if coming from a chunk of protein + sides format of most omni meals, the most successful veg dishes are not that seperate but rather all of the components cooked or served together
