Preheat oven to 400° F.
Place sliced onions in a jar or bowl and cover with vinegar. Set aside.
Place corn tortillas on a foil lined baking sheet, drizzle with 1 tablespoon olive oil (total) evenly rubbed into each tortilla. Sprinkle with cayenne pepper then bake for 5-8 minutes or until browned and crispy. Set aside to cool.
In a large mixing bowl add chopped romaine, black beans, avocado, radish, pumpkin seeds. Drizzle with remaining 3 tablespoons olive oil and lime juice over the salads and season with salt and pepper. Mix well to coat. Add chicken or shrimp if using and mix again.
Break up tortillas into bite size pieces and sprinkle over salad. Top with the pickled red onion and season with sea salt and a dash of cayenne. Serve immediately and enjoy!