Peel and wash the potatoes. Cut each in half lengthwise, then slice into thin half-moons. If you have small potatoes, you can slice them into circles. Peel and cut the onion in half, then slice it thinly into half-moon shapes as well.
Place the sliced potatoes in a bowl of cold water. Refrigerate for at least 30 minutes, or even overnight.
Drain the potatoes using a colander. For extra crispiness, spread them on a paper towel and pat them dry.
In a large skillet, add a generous layer of oil. Heat the oil well over medium heat. You can test it by adding a potato slice, it should sizzle right away.
Uncover, turn the heat on medium-high and cook for another 3 minutes flipping potatoes a few times until they get golden-brown and crispy. Turn off the heat, add salt, pepper and chopped dill on top. Enjoy immediately!
Add potatoes in an even layer. Let them fry undisturbed for 5–6 minutes to form a golden crust.
Spread sliced onions over the potatoes right before the first flip. Once well seared on the bottom, carefully flip with a spatula using as few motions as possible (1–2 big flips is ideal).
Cook for 4 more minutes, then flip once more. Cover the pan and cook over medium heat for another 3–4 minutes.
Remove the lid and continue frying uncovered for about 10 more minutes, flipping every 3-4 minutes to brown evenly and evaporate moisture. You can add more oil if the pan looks dry. Taste a piece. If it’s soft inside and golden outside, it’s ready. If not, continue frying uncovered until the potatoes are cooked.
Once cooked, season with salt, pepper, and optional fresh herbs or minced garlic. Remove from heat and serve hot!