• 2 oz. aromatic cheese that melts well, such as Raclette, Comté or Gruyère, coarsely grated
In medium bowl, use your fingers to mix the potatoes, lemon zest and rosemary until well combined.
In a 10-inch cast-iron pan, heat 5 tablespoons olive oil over high heat. Add potatoes, spreading them evenly and gently pushing them down with a spatula. Turn heat down to medium-high and cook for 5 minutes, reducing the heat if the potatoes brown too quickly.
Using a spatula, loosen the rösti from the sides of the pan and lift gently off the bottom. Then cover the pan with a large lid. Carefully and quickly flip the pan over. Keep the rösti on the lid while you add 1 tablespoon olive oil to the pan, then slide the rösti off the lid into the pan.
Cook for 5 minutes or until the potatoes are golden brown and crispy on the bottom. Take the pan off the heat and season the rösti to taste with salt and pepper.