In a small bowl or jar, whisk together the champagne vinegar, Dijon mustard, and maple syrup until combined.
Slowly drizzle in the olive oil while whisking continuously until the dressing is emulsified and slightly thickened. Season with salt and pepper. Set aside.
Assemble the salad:
Add the romaine, cherry tomatoes, red onion, and bell pepper to a large bowl. Toss until evenly distributed.
Drizzle with vinaigrette and toss to coat. Scatter parsley over the top. Serve immediately.
Notes
Dry romaine thoroughly after washing to prevent soggy salad.
Chop everything to a similar size so each bite gets a bit of everything.
Dress right before serving — this salad doesn't hold once dressed.
If red onion is too sharp, soak chopped pieces in cold water for 10 minutes, then drain and pat dry. Or you can also upgrade with sweet pickled onions.
No champagne vinegar? White wine vinegar or apple cider vinegar work in equal amounts.
Vinaigrette keeps refrigerated up to 1 week — shake or whisk before using.
Undressed salad keeps up to 2 days refrigerated; store components separately if possible.