A 3-day-old term newborn is brought to clinic for evaluation of a flat red lesion on the left side of the face that was present at birth. The lesion is a well-demarcated, blanchable erythematous patch that does not cross the midline and involves the forehead and upper eyelid. The infant is otherwise well-appearing. The parents ask whether the lesion will fade over time. Which of the following is the most likely diagnosis?