In a small saucepan combine 1/2 cup white wine vinegar, 1/2 cup water, 1 tbsp granulated sugar, 1/2 tsp kosher salt and 4 peppercorns (if using). Bring just to a simmer and stir until sugar and salt dissolve, about 1–2 minutes. Remove from heat.

Pour the hot brine over the sliced onion, press down so the onion is submerged, and let sit at room temperature until cool, about 20–30 minutes. The onions will be ready to use after 20 minutes but improve if left 1 hour. Store any leftovers refrigerated for up to 2 weeks.

Dressing

In a small bowl or jar combine 3 tbsp extra-virgin olive oil, 1.5 tbsp fresh lemon juice, 1 tsp honey (or maple syrup), 1/2 tsp Dijon mustard, 1/4 tsp salt and 1/4 tsp freshly ground black pepper.

Whisk vigorously (or shake in a lidded jar) until emulsified, about 20–30 seconds. Taste and adjust seasoning—add up to 1/2 tsp more salt or another 1/2 tsp honey if needed.

Salad Assembly

Prepare the produce: core and chop romaine to yield about 4 cups of chopped leaves. Seed and dice cucumber to make ~1 cup. Halve cherry tomatoes to make ~1 cup. Rinse blackberries gently and pat dry.

Drain the pickled red onion from the brine (reserve a tablespoon of brine if you want extra tang for the dressing) and slice any large rings into shorter strips so they disperse through the salad.

In a large bowl combine the chopped romaine, diced cucumber, halved cherry tomatoes, and blackberries. Add the pickled red onion and chopped parsley.

Add 3–4 tablespoons of the prepared dressing to the bowl (start with 3 tbsp). Toss gently but thoroughly to coat the ingredients. If you reserved a tablespoon of pickling brine, add 1 tsp to the dressing or salad for extra brightness.

Season with 1 tsp salt and 1/2 tsp freshly ground black pepper, tossing again and tasting. Adjust salt, pepper or additional dressing as desired.

Transfer to a serving bowl or individual plates. Sprinkle crumbled feta or goat cheese (about 1 oz) and 2 tbsp chopped toasted nuts over the top if using. Serve immediately.