Preheat your oven to 350°F/175℃
In food processor, combine 1 drained can of black beans, 1 undrained can of black beans, salt, onion powder, cumin, and garlic powder.
Process until smooth.
Heat olive oil in large non-stick over medium-high. Add bean puree to hot oil and fry for 10 minutes, stirring frequently.
Off heat, add dash of apple cider vinegar or lime juice.
Heat up the tostada shells in the preheated oven for 5 minutes.
Build the tostadas in such an order: tostada, bean puree, avocado, tomatoes, feta, then hot sauce.