Heat 1 tbsp olive oil over medium heat. Saute diced onion for 3-5 minutes until soft and translucent, then add garlic, cilantro, adobo seasoning, and oregano and stir for one minute. Pour in cider vinegar, black beans, and water. Bring to a gentle simmer and cook, covered, for at least 20 minutes. You can keep the heat very low and let the black beans cook for up to an hour to really incorporate all of the flavors. Just check the water level occasionally. Right before serving, squeeze lime juice into the beans and taste for salt and pepper.
At this point, preheat oven to 425.
Make the plantain chips. To cut a plantain, slice off the top and bottom, then carefully slice a slit from end to end with a sharp knife, piercing the skin all the way through but not cutting into the flesh. Slide a thumb beneath the slit on one side and carefully run the finger up and down the length of the plantain to loosen the skin. It might break off in pieces rather than unravel in one smooth motion. This is okay. Just be sure to get all of the skin off! You can also run the flat of the knife beneath the skin instead of your finger, but that scares the shit out of me and I'm likely to lose a digit if I do that.
Once the plantain flesh is cleared of skin, slice into 1/2 inch rounds.
In a small bowl, whisk together nutritional yeast, garlic powder, onion powder, cumin, chili powder, cayenne pepper, and salt. Set aside.
Prepare a plate with paper towels. Heat 1/4 cup high-heat oil in a skillet over medium-high. The oil should not smoke overmuch. In batches as needed, set rounds into the skillet and cook 2-3 minutes per side until golden. Transfer to paper towel lines plate to drain. Repeat with any remaining plantains.
Prepare a fresh plate with paper towels, or replace the oily towels from the plate you were using. Cover the bottom of a glass or jar with brown paper (from a paper bag or similar) and press each round to flatten. Once all are pressed, fry an additional 2 minutes per side. Set on the new plate to drain once more. When cool enough to touch, toss with the nacho spice blend until thoroughly coated. Cover and keep warm.
Make the tostadas. Brush both sides of each tortilla with oil and set on one or two large baking sheets. Bake 6-8 minutes per side. Sprinkle cheese evenly over each tostada, then return to oven and bake about 5 minutes more until cheese melts and bubbles.
To assemble, top each cheesy shell with black beans, then garnish with cilantro slices, a sauce of choice, and lime juice. Nestle two or three plantain chips into the beans. Eat the rest.