Preheat the oven to 110 °C (225 °F). In a stand mixer, beat the egg whites until firm peaks form while gradually adding the sugar. Combine a quarter of the meringue with 100 g (1/2 cup) of the reserved cranberry purée. With a spatula, gently fold in the remaining meringue. With an offset spatula, spread the mixture 5-mm (1/4-inch) thick on a silicone pastry mat. Separate the meringue sheet into four equal parts by making a cross with the end of a wooden spoon, for even baking. (The four pieces should not touch.)
