To make the filling, warm the olive oil in a medium-sized pot over medium heat. Sauté onion and garlic with a dash of salt for 4 to 5 minutes, until the onions are softened and turning translucent. Add tomato paste, cumin, and chili powder and sauté for another minute.

Add quinoa and 1 cup broth. Bring to a gentle boil, cover, reduce to a simmer, and cook for 15 minutes. Remove from heat and let it rest, covered, for 5 minutes. Uncover, drain any excess liquid, fluff quinoa, and stir in black beans, salt, and pepper. Cover and set aside to warm beans.

To make the avocado sauce, combine ingredients in a food processor or blender, blending well and seasoning with salt and additional lime juice as desired.

In a large skillet over medium heat, warm tortillas in a single layer, flipping halfway. Wrap in a tea towel until ready to serve. To assemble, spread filling in the center, drizzle with avocado crema, top with romaine and any additional garnishes.