In a bowl, beat the egg whites on a low - medium speed until foamy. Add the cream of tartar and continue beating until soft peaks get formed.
Add the sugar little by little and continue beating until the meringue holds very stiff peaks. Add the vanilla extract, mix well.
Place the meringue in a pastry bag fitted with a 1 cm tip.
Make high mounds of meringue (in a lined baking tray) and bake in a previously pre-heated oven at 100°C for 2 hours.
Turn off the oven, open slightly the door and leave the meringues in the oven drying several hours.
Decorate with the nutella.