Chop the iceberg lettuce into small pieces (about quarter-size) and place in a large bowl.
Slice the red onion as thin as possible, then soak in cold water for 10 minutes to mellow the flavor. Drain well and pat dry.
Cube the salami, pepperoni, turkey, and provolone cheese into small, uniform pieces (about dime-size).
Quarter the grape tomatoes and chop the banana peppers. Reserve 1 tsp of banana pepper juice for the dressing.
Make the dressing: In a small bowl or jar, combine mayonnaise, apple cider vinegar, banana pepper juice, garlic powder, oregano, salt, and black pepper. Whisk or shake until smooth and well combined. Taste and adjust seasonings as needed.
Add all the chopped meats, cheese, tomatoes, onions, banana peppers, and parmesan to the bowl with the lettuce. Toss gently to distribute evenly.
Pour the dressing over the salad and toss thoroughly until every ingredient is well coated.
Serve immediately for maximum crunch, or let sit for 5 minutes to allow flavors to meld.