Preheat oven to 350˚F. Spray a 8 or 9-inch quiche dish with cooking spray or lightly grease with vegetable oil.
Heat olive oil in a large sauté pan over medium heat. Add prosciutto and stir for 1-2 minutes. Add garlic and rosemary and cook for another 30 seconds. Add spinach and cook just until spinach is beginning to wilt. Turn off heat and set aside. Spinach will continue to wilt.
Place Greek yogurt in a large bowl and whisk until smooth. Add eggs, two at a time, whisking after each addition until smooth. Add cheese, lemon zest, salt and pepper. Stir to combine.
Pour egg mixture into the prepared quiche dish. Top with spinach proscuitto mixture (much of the spinach mixture will sink into the eggs).
Bake in preheated oven until eggs have set, about 40-45 minutes. Allow to cool for 10 minutes before serving.
Notes
*I love the Stockmeyer prosciutto from Trader Joe's.It's very lean, mildly smoked and has great flavor!Costco also has a wonderful smoked prosciutto, as I'm sure many other stores do too.**Gruyere cheese can be quite pricey but you don't need much for this recipe and it really adds a ton of fabulous flavor.Trader Joe's has a domestic Gruyere which is very reasonably priced along with being very tasty.