Sift the flour and salt together. Form into a pile on the counter or a cutting board. Make a well in the middle of the flour.
Crack the egg into a measuring cup. Whisk the egg, then add cold water to the cup to bring the total measurement up to 1/2 cup. Whisk again.
Pour the egg mixture into the well of dough. Use a fork to slowly combine the flour into the egg, grabbing from the center and slowly working outwards.
When the dough becomes too thick to mix with a fork, begin kneading with your hands. Knead until smooth, adding more water if necessary. Cover and rest for 30 minutes.