Trim and discard any browned edges from the romaine hearts. Chop or tear the romaine into roughly 1- to 1½-inch pieces. Rinse thoroughly under cold water if not pre-washed, then spin in a salad spinner or pat dry with clean kitchen towels until mostly dry. Place the cleaned lettuce in a large mixing bowl.

Prepare cucumber

If desired, peel the cucumber. Slice it in half lengthwise and cut into 1/4-inch half-moon slices. Add the cucumber slices to the bowl with the lettuce.

Prepare tomatoes

If using cherry or grape tomatoes, halve them. If using larger tomatoes, core and dice into bite-sized pieces. Add the tomatoes to the bowl.

Prepare red onion

Peel and cut the red onion into very thin half-moon slices. If you want a milder onion flavor, soak the slices in cold water for 5 minutes, then drain and pat dry. Add the onion to the bowl.

Toppings

Add the croutons to the bowl right before serving so they remain crunchy. Reserve the chopped parsley for garnish.

Season the assembled salad lightly with the measured salt and freshly ground black pepper, tossing gently to distribute.

Dressing

Dress and toss

If using store-bought ranch, transfer the measured cup to a small bowl and whisk in the optional teaspoon of lemon juice or vinegar to brighten the flavor. Taste and adjust. Pour the ranch over the salad just before serving — start with about 3/4 cup and add more to taste. Toss gently but thoroughly so all vegetables are lightly coated.

Plate and finish: Portion the tossed salad into 4 bowls or plates. Sprinkle the croutons and chopped parsley on top and finish with a final grind of black pepper. Serve immediately.