Blend the butternut squash and the yogurt with an immersion blender.
Beat the eggs and sugar with the electric whisk, then add the melted butter.
Stir in the butternut purée, then fold in the flour sifted with potato starch, baking powder and nutmeg.
Grease and dust lightly with flour a 24 cm large ring cake pan. Scrape the batter into the pan.
Bake the cake in the preheated oven for about one hour until golden brown and dry inside. Remove the cake from the pan and let cool down completely on a wire rack. Dust with icing sugar before serving.
Recipe by Juls' Kitchen at http://en.julskitchen.com/breakfast/butternut-squash-cake