Make the Pickled Onion (Optional): If you're making the quick pickled red onion, prepare that first. In a small pot, add vinegar, water, salt and sugar. Bring mixture to a boil to dissolve salt and sugar. Remove pot from heat. To a medium bowl or large glass jar, add the onions, then pour the hot pickling liquid over top. Set aside for at least 30 minutes to pickle.
Make the Cabbage: Add the cabbage to a bowl with the juice from 1 lime and a spinkle of salt. Squeeze the cabbage with your hands a few times to massage and tenderize. Set aside while you prepare the black beans.
Cook the Onion: In a large skillet, heat 2 tsp oil (or use water for oil-free) over medium heat. When the pan is hot, add the onions. Season with salt. Cook for 4-6 mins, stirring occasionally, until tender.
Add Seasonings: Add the garlic, cumin, chipotle pepper and adobo sauce. Stir well and cook for 1 minute to toast.
Add Black Beans and Water: Add the canned beans, including the liquid from one of the cans, along with 1/4 cup of water. Stir well to combine. Cook for 6-8 minutes, mashing some of the beans with a potato masher or the back of a fork or wooden spoon, until thickened. Season to taste with salt, if needed.
Make Cilantro Lime Crema (Optional): Using a blender, blend the tofu, garlic, cilantro, lime and salt, until smooth. Add 1-2 tbsp of water, if needed, to achieve a smooth sauce or thinner crema, if desired.
Warm Tortillas (Optional): Warm the tortillas in a large skillet over medium heat or briefly on a gas stove over open flame. Cook them in batches, flipping to warm and toast each side. Cover with a clean tea towel to keep warm until ready to serve. You can also warm them briefly in the microwave.
Assemble Tacos: To the warmed tortillas, add a scoop of black beans, then top with the cabbage, crema, pickled red onion and fresh cilantro, if desired.