Whisk together red-wine vinegar, minced garlic clove, sugar, salt, and black pepper in a small bowl.

Gradually whisk in extra-virgin olive oil until well combined to create the vinaigrette.

Bring water, red-wine vinegar, sugar, and salt to a boil in a saucepan.

Add thinly sliced red onion and simmer until crisp-tender, about 3 minutes.

Drain the onions and allow them to cool.

Tear romaine lettuce into bite-size pieces and spread them on a large platter.

Scatter fresh flat-leaf parsley leaves, roasted red peppers, marinated artichoke hearts, assorted brine-cured olives, drained peperoncini, halved cherry tomatoes, and the cooled pickled red onion over the romaine lettuce.

Whisk the vinaigrette again to ensure it's well combined.

Drizzle the vinaigrette evenly over the salad.

Serve immediately.