3 medium zucchini
1/4 teaspoon salt
1 large Yukon Gold or Yellow Finn potato , peeled and cut into eighths
1 tablespoon olive oil
5 large eggs, lightly beaten
1/4 teaspoon freshly ground black pepper
1/4 pound creamy feta, crumbled
1 cup Monterey Jack cheese
Trim the zucchini at both ends. Quarter them lengthwise and cut out and discard the column of seeds on each piece. Use the grating disk on a food processor or a hand-held grater to grate the zucchini.
Transfer the grated zucchini to a colander set inside a bowl, sprinkling salt between the layers. Set a small plate on top of the zucchini to press it down. Set aside for 15 minutes to drain . When ready, squeeze the zucchini with your hands to remove any excess water.
Place the potato pieces in a small saucepan and cover with cold water by about an inch. Bring to a boil, lower the heat to a simmer, and cook for 12 to 15 minutes, or until tender.
With a slotted spoon, transfer the potato to a bowl and mash it with a fork until it is almost smooth. Leave to cool. While the potato cooks and cools, preheat oven to 375F. Use the olive oil to coat the bottom and sides of a 9-to 9 1/2-inch pie pan. Set the pan on a rimmed baking sheet to catch any drips, then place both inside the oven to warm for at least 5 minutes.
Mix the eggs, black pepper, feta cheese, and 3/4 cup of the Monterey Jack cheese into the cooled mashed potatoes. Stir in the drained and squeezed zucchini.
Carefully remove the hot pie pan and baking sheet from the oven. Pour the zucchini mixture in the hot pie pan, smoothing the top. Sprinkle with the remaining 1/4 cup Monterey Jack cheese.
Return the pie pan and the baking sheet to the oven and bake for 35 minutes or until the top is brown and the frittata is set in the middle.
Let the frittata cool for 5 minutes before cutting into wedges. Leftover frittata will keep for up to a week in the refrigerator; eat cold or briefly warmed in the microwave. .