Remove outer wilted leaves from the iceberg head. Quarter the head, remove the core, then thinly slice or chop to yield about 6 cups of crisp bite-sized pieces. Rinse under cold water and spin or pat dry thoroughly.

Prepare tomatoes

Core and cut the tomatoes into 1/2-inch dice (or into wedges if preferred) to make about 1 cup. Drain any excess juices so the salad doesn't become watery.

Prepare cucumber

Peel if desired, slice cucumber lengthwise and scoop seeds if watery. Chop into 1/4-inch half-moons to make about 1 cup.

Prepare shredded carrot

If not using pre-shredded carrot, peel and grate 1 large carrot on the coarse side of a grater to yield about 1 cup. Pat dry if it seems wet.

Segment lemons

Cut one lemon into 4 wedges (use 2 wedges for serving). Keep wedges chilled until serving.

Combine the lettuce, tomatoes, cucumber, and shredded carrot in a large mixing bowl and toss gently to distribute evenly. Chill while you prepare the dressing or dress immediately according to preference.

Homemade garden sauce

Combine base ingredients

In a small bowl or jar, add 1 tablespoon mayonnaise and 2 tablespoons plain yogurt (or sour cream). Whisk until smooth.

Add flavorings

Whisk in 1 teaspoon olive oil, 1 teaspoon fresh lemon juice, 1 teaspoon apple cider vinegar, 1 teaspoon honey, and 1 teaspoon Dijon mustard until fully combined.

Herbs and aromatics

Stir in 1 tablespoon finely chopped fresh parsley, 1 teaspoon finely chopped chives, and 1/2 teaspoon minced garlic.

Season and adjust

Add 1/2 teaspoon salt and 1/4 teaspoon freshly ground black pepper. If the dressing is too thick, thin with up to 1 teaspoon water, whisking to the desired consistency. Taste and adjust seasoning with more lemon juice, honey, or salt as needed.

Chill

Cover and refrigerate the sauce for at least 10 minutes (or up to 2 hours) to let flavors meld. Shake or whisk again before serving.

Dress and serve

Just before serving, either drizzle 2–3 tablespoons of the garden sauce over the prepared salad and toss gently to coat, or serve the sauce on the side so diners can add to taste. Garnish with lemon wedges alongside. Serve immediately.