Curry curry curry. I'll make a big batch of lentil or bean curry using lots of onions and whatever tomatoes are about to go (or were bought and found out to be watery, tasteless sad bois). A lil tempered whole spices, some garam masala, onions, tomatoes (and or peppers), cooked well with most any legume in a pressure cooker, makes a huge amount of healthy tasty food cheaply. I'll thicken it with shredded coconut and toss in fresh herbs or dried methi.
Lunch for 2 weeks, just add fresh rice. I'll freeze half and thaw for the following week or another if I'm craving more variety.
Edit: if you're not buying your spices at an Indian grocery and you have access to one, you're drastically overspending on spices. I buy 250g of whole cumin for under $2. That'll cost you five fold that from McCormick's or what have you.
Edit2: of course meat curries are possible, too. They cost a lil more, but still a great way to stretch your dollars while eating healthy and deliciously.
It's hard to math out exactly due to all the spices, (I'll use coriander, cumin, cardamom, mustard, ginger, garlic and garam masala in most curries) but the major cost drivers are the beans, tomatoes and onions. I'll use 3 medium onions for half a pound of beans and around 6 tomatoes/peppers. This'll make around ten to fifteen lunches, depending on your portion size (I usually bring rice and a veg with mine, but sometimes I don't have a roasted veggie ready). I haven't done the exact math since before the pandemic, but then I estimated it at $0.80 a meal, so it's probably closer to $1.40 now.
Edit: pricing is for the bean/lentil curry (masoor or chana dal are my typical go tos, but I'll usually throw in some urad dal and I've used fava beans with success). Chicken curries bring up the cost, but not significantly.
It takes some practice to get the amount of baking soda and cook time down for each bean, as it's slightly different, but if I over cook the beans, I just make a blended bean dish instead of a whole one.
This trick DOESN'T work for hummus, don't bother. If you're making hummus, soak your chickpeas overnight (6-8 hrs, longer is okay as long as they don't sprout) instead. It's hard to nail the texture otherwise.