How to Make It
In a small saucepan, bring the vinegar, sugar, water and salt just to a boil, stirring to dissolve the sugar. Remove from the heat; add the onion. Let cool, then refrigerate until chilled.
In a small bowl, whisk all of the ingredients together and season with salt and pepper.
In a medium bowl, toss all of the cucumbers with the vinegar and the 2 tablespoons of olive oil. Season with salt and pepper and let stand for 5 minutes.
Spoon the dressing into shallow bowls and top with the cucumber salad. Drain the onion and scatter over the salad. Garnish with sunflower sprouts and seeds, tarragon and a drizzle of olive oil. Serve.