Preheat your oven to 400°F / 200°C. 2.
In a large bowl, toss the diced potatoes and onions with olive oil until evenly coated.
Spread them in a single layer on a large, rimmed baking sheet.
Roast for 25-30 minutes, tossing halfway through, until the vegetables are tender and beautifully browned at the edges.
Remove from the oven, sprinkle with salt and pepper, and set aside to cool slightly. 3.
While the vegetables cool, reduce the oven temperature to 325°F / 165°C (or 300°F / 150°C for a glass pie plate). Generously butter a 9-inch pie plate or similar oven-safe pan. 4.
In a large mixing bowl, whisk the eggs until they are light and frothy. Gently fold in the cooled potato and onion mixture, along with the grated smoked cheese.
Pour the entire mixture into your prepared pie plate. 5.
Bake for 25-30 minutes, or until the frittata is set and the center is just barely jiggly. A knife inserted near the center should come out mostly clean.
Let it rest for a few minutes before slicing and serving.
Don't be afraid to swap the cheese. If you don't have smoked Gouda, crumbled goat cheese, sharp cheddar, or even feta are delicious alternatives that bring their own unique character to the dish.
