Peel and chop the onion. Peel and chop the purple sweet potatoes into approximately 1/2 inch squares. The smaller the pieces, the quicker they cook. And, drain and rinse the canned black beans.
Heat the oil in a large skillet over medium heat. Add the chopped onion and sauté for about 7 minutes until soft and slightly golden brown.
Add the peeled and chopped purple sweet potatoes to the skillet.
Pour in 2 tablespoons of water, cover the pan, and pan fry these potatoes for 4 minutes over medium heat.
Uncover, stir well, add another tablespoon of water, then cover again and roast for about 2 minutes, or until the sweet potatoes are fork-tender. If they are cut small enough, the purple sweet potatoes will cook in about 6-7 minutes.
Stir in the harissa, cinnamon, and drained black beans to the roasted sweet potatoes and black bean mixture. Cook for about 1 minute until fragrant.
Then fold in the garam masala, stirring well to coat the ingredients evenly. Season generously with salt and pepper to taste. Toss on some chopped cilantro.
Pile the sweet potato black bean filling into warm tortillas and top with your favorite toppings. Or, enjoy these in bowls with chopped celery, avocado, tomatoes, and tofu or chicken.