Spicy Chicken and Cabbage Salad

Name: Spicy Chicken and Cabbage Salad
Ingredients: 1 small red onion; 2 skinless, boneless chicken breasts (about 1 pound, 5 ounces); 3 garlic cloves, smashed; 1 red chile, halved, thinly sliced, divided; 2 cups cilantro leaves with tender stems, divided; 1 tablespoon Diamond Crystal or 1¾ teaspoons Morton kosher salt, divided, plus more; 3 tablespoons vegetable oil; ⅓ cup peanuts, preferably skin-on; Juice from 1 lime (about 2 tablespoons); ½ medium head of green cabbage, very thinly sliced; 2 medium Persian cucumbers, thinly sliced on a bias