A shrub--a sweet-tart infusion of vinegar and fruit--adds complex flavors to this easy dressing by Mary Karlin, author of Mastering Fermentation. Karlin especially likes the dressing over a salad of romaine, radicchio, red onion, avocado, feta, and toasted pumpkin seeds.
In a small bowl, whisk together shrub and lime juice. Stir in shallot. Vigorously whisk in oil in a stream. Whisk in salt and pepper. Taste with a piece of lettuce; add more lime juice, salt, and pepper as needed.