These are for hot rather than cold burritos.
Fry Onion(s) in a moderate amount of oil
chuck in spices etc, I normally lob in Paprika, cumin, coriander, garlic powder, chilli flakes, salt pepper whatever really
Once softened add beans – I’ve done this with 1-3 cans of beans, usually kidney, borlotti canellini black, most beans work
Fry beans over a moderate heat for a few minutes, add a small amount of stock (I’m sure water would do too)
simmer moderate heat until beans are soft/softening
mash those mofos
spoon into a wrap add cheese and grill (you can bake them too if you’re making a load, although it means you cant’s add extra topping easily) add extra fillings
Be interesting to see if you can make these as a microwaveable lunch – never done it meself