Slice the onion in half, then cut it into very thin slices. Peel the potatoes and slice them very thin as well. Slicing the onion thinly will help it almost melt during cooking.

Add the olive oil, onion, and potatoes to a cold skillet. Add salt right away—don’t be shy, as it will help draw out moisture from the onion.

Turn the heat to high and let the pan get hot. Stay close so the potatoes don’t stick or burn. Once the pan is hot, lower the heat slightly and cook for at least 15–20 minutes without a lid. You don’t need to add water; the potatoes will cook in the moisture released by the onion. If a bit of crust forms, that’s great—just stir occasionally.

Meanwhile, beat the eggs with the grated cheese (I used 15-month aged Parmesan, but use whatever you like) and a pinch of salt. You can also add your favorite dried herbs (like thyme, rosemary, marjoram, oregano), but I recommend using dried herbs so they don’t turn bitter in the oven.

Here’s my little secret: add a scant 1/2 teaspoon of baking soda and gently mix it in. This will help the frittata rise in the oven and make it light and fluffy inside!

Once the potatoes and onions are ready, preheat the oven to 480°F (250°C). While the oven heats, let the potato mixture cool a bit before adding it to the eggs.

Combine the potatoes with the eggs, mix well, and pour into a baking dish with high sides (avoid a loaf pan, as it may not cook through in the center). Place in the middle rack of the oven. After a few minutes, when the top starts to set, take it out and sprinkle more grated cheese on top. Return to the oven, switch to broil, and move to the top rack. Let it form a beautiful golden crust.

When it’s done, take it out, place it on a cutting board, and let it rest for about 30 minutes before serving. The best part? It tastes even better the next day! Enjoy and see you next time!