Place a 10-inch cast iron skillet over medium low heat for 5 minutes.
While the pan is heating, grate the potato on the largest hole of a box grater. Squeeze the grated potatoes in a tea towel to remove excess moisture.
Add the fat to the pan and scatter evenly with the potatoes. Sprinkle with salt and cook for 5 minutes without disturbing. Decrease the heat to low, flip the potatoes, and cook for another 5 minutes. Serve immediately.