In a large bowl, whisk the egg whites vigorously until very frothy, then whisk in the almond and vanilla extracts.
Fold in the sugar, almond meal, and salt, to form a soft, sticky dough.
Line 2 baking trays with parchment paper and place the granulated sugar (for coating) in a bowl. Scoop the dough into 25 g portions. Lightly dampen your hands to prevent the dough from sticking, then roll each portion between your palms to form a smooth ball. Roll each ball in the sugar to lightly coat, then place on a baking tray. Press your thumb into the centre of each dough ball to make a deep indent.
Chill the cookies on the trays for 60 minutes. Meanwhile, preheat the oven to 170°C (150°C fan/340°F).
Use a fine-mesh sieve to dust the cookies with icing sugar. Bake for 17–20 minutes, until they look puffed, slightly cracked, and mostly set. They should still be quite pale when you take them out, with lightly golden bottoms.
Allow to cool on the trays for 5 minutes, then transfer to a wire cooling rack.
Once the cookies are completely cool, spoon about ½-1 teaspoon of cherry jam into the centre of each.