Reduce the heat to maintain a gentle simmer. Add the lemon juice, remaining 1/4 teaspoon kosher salt, remaining 2 tablespoons unsalted butter, and 3 tablespoons drained nonpareil capers, and stir to combine. Once the butter is melted, return the chicken and any accumulated juice on the plate to the pan. Simmer until the chicken is cooked through and registers at least 165ºF on an instant-read thermometer, 4 to 6 minutes. Taste and season with more kosher salt as needed. Garnish with the parsley.
