Adapted From: The Kitchn (originally from Serving Up the Harvest)
1 medium zucchini or yellow summer squash, thinly sliced
1 tsp Salt
4-5 tablespoons extra-virgin olive oil, or more as needed
1 1/2 pounds waxy potatoes, thinly sliced
1 large onion, halved and thinly sliced
1/4 pound smoked Canadian bacon or ham, diced (I used 2 roasted garlic chicken sausages)
6 eggs (I used a combination of whole eggs and bottled egg whites)
Freshly ground black pepper
(other seasoning to taste - I used a few dashes of Penzey's shallot-pepper mix)
1 cup grated Cheddar (I used fontina)
1. Combine the zucchini and 1 teaspoon salt in a colander and toss well. Set aside to drain for 30 minutes.
2. Heat 3 tablespoons of the oil over medium-high heat in a large, well-seasoned cast-iron skillet or ovenproof nonstick skillet. Add the potatoes and onion, reduce the heat to medium-low, and cook, flipping and stirring occasionally, until the potatoes are soft, about 20-30 minutes. Increase the heat to medium-high and continue cooking, tossing occasionally, until the potatoes are are brown, about 5 minutes. Remove the potatoes with a slotted spoon but keep the skillet on the burner.
3. Transfer the zucchini to a clean kitchen towel and pat dry. Add the zucchini and Canadian bacon or sausage to the skillet and sauté over medium-high heat, until the zucchini is just tender, about 4 minutes. Remove the zucchini and Canadian bacon with a slotted spoon. Keep the skillet over the heat.
4. Beat the eggs and pepper (and any other seasonings) to taste in a medium bowl until well blended. Fold in the potatoes, zucchini and Canadian bacon, and cheese.
5. Preheat the oven to 350°F. Add 1 to 2 tablespoons of the remaining oil to the skillet as needed to lightly coat the bottom. Pour in the egg mixture, reduce the heat to medium-low, and cook without stirring until the bottom is set, about 10 minutes.
6. Transfer the skillet to the oven and bake until the top is set, 5 to 15 minutes, checking every 5 minutes.
7. Place a serving plate on top of the skillet and carefully invert. The frittata should fall out of the pan. Cut into wedges and serve.