In a jar with a lid, add the lemon juice, mustard, vinegar, sugar, oregano, olive oil, kosher salt, and black pepper. Add the lid and shake for 10 seconds until all ingredients are thoroughly combined. Taste and adjust seasonings.

Add the chopped romaine to a large bowl and drizzle with a few tablespoons of dressing.

Top the romaine with the red onion, chickpeas, cherry tomatoes, mozzarella, pepperoncini, roasted red peppers, and basil. Stir together well before serving. Add more dressing, if desired.

Serve the salad in bowls on its own or with pasta or pizza.