Zucchini-Potato Frittata

1 medium or 2 small zucchini, sliced
Salt
4-5 tablespoons extra-virgin olive oil
1 1/2 pounds potatoes, thinly sliced
1 large onion, halved and thinly sliced
1/4 pound Canadian bacon or ham, diced
6 eggs
Freshly ground black pepper
1 cup grated Cheddar

Preheat oven 350º. Combine zucchini and 1 tsp salt in a colander; toss well. Set aside to drain for 30 min. Heat 3 Tb. the oil over med-high heat in a large cast-iron skillet or ovenproof nonstick skillet. Add potatoes and onion, reduce heat to med-low, and cook, flipping and stirring occasionally, until potatoes are soft, about 20 min. Increase the heat to med-high and continue cooking, tossing occasionally, until the potatoes brown, about 5 min. Remove potatoes with a slotted spoon but keep skillet on the burner. Transfer zucchini to a clean kitchen towel; pat dry. Add zucchini and Canadian bacon to the skillet; sauté over med-high heat, until zucchini is just tender, about 4 min. Remove zucchini and Canadian bacon with a slotted spoon, keeping skillet over the heat. Beat eggs and pepper to taste in a  bowl until well blended. Fold in potatoes, zucchini and Canadian bacon, and cheese. Add 1-2 Tb of the remaining oil to skillet as needed to lightly coat bottom. Pour in egg mixture, reduce heat to med-low, and cook without stirring until the bottom is set, about 10 min. Transfer skillet to oven; bake until top is set, 5-15 min. Check every 5 min. Place a serving plate on top of the skillet and invert the frittata onto it. Cut into wedges and serve. From Serving Up the Harvest  by Andrea Chesman.