I just volunteered to make lunch for someone who is vegetarian and can’t eat dairy, peanuts, or legumes. What am I gonna do? Dopers, help me out with recipes here!
Make a delicious soup and serve it with fresh-bought bakery bread.
Pasta with marinara sauce.
The aforementioned soup.
Veggy sandwich on fresh-bought bread.
Salad with grilled veggies and sunflower seeds.
Veggy stir-fry with tofu.
Soft tacos with a filling made from roasted peppers (as hot as she likes) and mushrooms, with salsa.
Tomatoes, eggplant, and zuchinni sauteed in olive oil with garlic, served over soft polenta.
Something with winter squash - winter squash roasted and stuffed with rice & mushrooms, winter squash sliced and made into soft tacos, soups, etc.
Preheat oven to 425 or so and heat a rimmed backing sheet (lined with foil for easy cleanup).
Peel & cube butternut squash. Toss with olive oil, salt, and some seasonings (curry powder is one good option, or you can go the herb route - thyme, rosemary, etc.) and spread onto hot baking sheet. After about 20 mins. or so, stir and add chunks of onion. Continue roasting until veggies are starting to carmelize and turn golden brown.
Make a stuffing out of some grain (quinoa, couscous, rice, what have you) and season it well. Take the tops off some of those hard, tasteless tomatoes you get this time of year. Salt insides of tomatoes very well and let drain upside-down for 10-20 mins. Stuff with seasoned grains and top with breadcrumbs. Broil until tops are golden brown. The tomato gets all roasty-sweet and tasty! 
ETA: not that these two would necessarily go together. Just the first two recipes that popped into my head. You can also blender-ify the roasted squash and onions into a lovely, thick soup as suggested above.
I know lentils are in the legume family but they’re a different genus and species from “regular” beans (kidney beans, black beans etc.), so it’s conceivable that this person might be able to eat them (but ask before offering!!).
If so, Epicurious has a yummy barley, lentil and swiss chard soup. Add extra tomatoes, use vegetarian vs. chicken broth, and reduce the swiss chard (I found too much overwhelms the stuff).
Also find out if the person can eat eggs. Some people lump that in with “dairy” though others will eat one or the other but not both.
Maybe look at vegan recipes
Watch for hidden dairy on anything packaged. Bread especially.
Another vote for a big pot of soup: could be vegetarian veggie, veg chili… endless possibilities with that. Serve with high-quality crackers or fresh bakery bread and a nice salad.
BTW, when, where and what time is this lunch? I’d like to know when I should show up. Don’t worry, I’ll bring dessert…
Ask whether the problem with dairy is dairy allergy or lactose intolerance: if it’s allergy, eggs are most likely also out.
While some folks who are allergic to milk products are also allergic to eggs, that’s not something can you assume. They’re completely different, chemically.