Preheat the oven to 400°F and prepare a springform pan, lightly greased with butter.

Prepare the vegetables: cut the zucchini, mushrooms, and red bell pepper into small to medium pieces. Peel the onion and garlic and finely chop them.

Heat a splash of olive oil in a skillet and add the chopped onion and garlic. Sauté briefly until translucent.

Add the sliced mushrooms, zucchini, and red bell pepper to the pan. Cook everything over medium heat for a few minutes, stirring regularly.

Season with salt and pepper while cooking.

Crack the eggs into a mixing bowl and add the mascarpone. Whisk until smooth. Season the mixture with a little pepper and add the grated Emmentaler cheese. Stir everything together well until you have a fluffy mixture.

Spoon the cooked vegetables into the springform pan, making sure to include as little liquid as possible. Tear the slices of Prosciutto di Parma over the vegetables in the springform pan.

Pour the egg mixture evenly over the vegetables and let it sit for a moment so it sinks well into the springform pan.

Place the springform pan in the preheated oven and bake the frittata for 25 minutes, or until the top is nicely browned.

Remove the springform pan from the oven and let the frittata cool for a few minutes so it can set a little further. Enjoy!