Pickled Vegetable Lettuce Cups

Name: Pickled Vegetable Lettuce Cups
Ingredients: ¼ cup apple cider vinegar; 2 tablespoons white wine vinegar; 1 tablespoon kosher salt, plus more; ½ fennel bulb, thinly sliced; 1 small shallot, thinly sliced; 1 baby beet, trimmed, scrubbed, very thinly sliced; 2 radishes, trimmed, thinly sliced; ⅓ cup buttermilk; ⅓ cup whole-milk plain yogurt; 1 tablespoon fresh lemon juice; Freshly ground black pepper; 4 heads of Little Gem lettuce, leaves separated, or 1 head of romaine, leaves separated, cut in half crosswise; ½ cup cilantro leaves with tender stems; ¼ cup torn mint leaves