Preheat the oven to 425 degrees F. Line a sheet pan with parchment paper.
In a large bowl, stir the chickpeas and red onions with 2 tablespoons olive oil, cumin, chili powder, garlic powder, paprika, oregano, 1 teaspoon kosher salt and 1/2 teaspoon black pepper. Once they are coated in the spiced oil mixture, smash the chickpeas and onions with a fork.
Warm the tortillas, wrap them in a damp paper towel. Microwave for 30 seconds. This steams the tortillas, so then you can fold them to assemble the tacos.
Brush each tortilla with olive oil on both sides. Spoon the chickpea filling onto one half of each tortilla (about 1/3 cup, not packed). Then sprinkle the filling with cabbage and about 1 tablespoon cheese. Fold over the taco and gently press it down. Repeat for the remaining tortillas.
Bake the tacos 5 minutes. Then flip them over. Bake for another 10 minutes. Flip them again and bake for 5 minutes until they are golden brown and crisp on the outside.
To make the avocado tahini sauce, combine the avocado, tahini, lime juice, water, cilantro leaves and pinches of salt and pepper in the bowl of a food processor or a blender. Puree until smooth. (You may need to add another tablespoon of water to thin it out.)
Arrange the tacos on a serving plate. Top with chopped cilantro and serve with the avocado sauce on the side or drizzled over the tacos.