So you get creative. And maybe you have to throw in an under-appreciated starchy vegetable. And maybe, just maybe, you've been playing with some of the more esoteric uses of a food processor. You might come up with something like this.
Part the first: a bean salad.
In a large bowl, combine 2 cans or 1lb of (soaked, cooked, etc) black beans, well-drained. Throw in a a can of corn. Perhaps pull out a can of olives, slice that up, and add. While you're on knife work, dice a red onion finely -- and half a medium jicama, a bit less fine.
Set that aside; it won't need dressing for these purposes and you'll have plenty of leftovers that you can dress as you go.
Part the second: purée. In a food processor, combine the following:
- 1 avocado
- a modest amount of corn or olive oil
- a dash or two of red wine vinegar
- juice (and pulp; why not) of 1 lime
- red pepper flake to taste
- small amounts of garlic (powder is fine here)
- a pinch of salt
Blend that puppy until smooth. If you need a bit more liquid, add either oil or vinegar based on taste and overall texture. Oh, and if you're making ahead or in a large batch, be sure to retain an avocado pit to keep from browning before serving.
And that's it. Toast yourself up some corn tortillas, layer on the purée, bean mixture, and whatever loose greens you have around. You might note that this is not just vegetarian at this point, but also vegan. Feel free to keep it that way -- or sneak in cheese and yogurt. And there you go: interesting tacos that don't depend on all the usual ingredients.