Peel, seed, and cut zapallo into chunks. Place in a saucepan, cover with water, and bring to a boil over medium-high heat. Cook until zapallo is soft and easily pierced with a fork, 15 to 20 minutes. Drain and allow to cool slightly.

Mix flour, baking soda, and salt together in a mixing bowl, and set aside. Stir together squash and melted butter. Stir the flour mixture into the butter mixture until blended. Turn the dough out onto a lightly floured surface and knead until soft and satiny, adding a little more flour if necessary. Cover dough with a towel and allow to rest 15 minutes.

Roll out the dough to 1/8-inch thick, and cut into 3-inch diameter circles. Poke each circle a few times with a fork to make holes and prevent rising.