Combine the barley, water, cumin, chili powder, salsa, and salt in the Instant Pot and stir to combine. Secure the lid and move the steam release valve to Sealing. Select Manual/Pressure Cook and cook on high pressure for 20 minutes. Let the pressure naturally release for 10 minutes.
While the barley is cooking, prepare the vinaigrette. In a pint-sized mason jar, combine the olive oil, vinegar, lime juice, maple syrup, garlic, cumin, cayenne, salt, and several grinds of pepper. Screw on the lid and shake vigorously to combine. Set aside.
When the screen reads L0:10, move the steam release valve to Venting to release any remaining pressure. When the floating valve drops, remove the lid and stir in the black beans to create the taco “meat.” (If using canned beans, drain and rinse them first.)
To serve, place the romaine, cabbage, tomatoes, green onions, cilantro, and barley and black bean mixture in a serving bowl. Generously drizzle the lime vinaigrette on top, add a sprinkling of cheese and avocadeo slices, and serve right away. Store leftovers in three separate airtight containers—one each for the “meat,” the dressing, and the chopped vegetables—in the fridge for 5 days.