1) Cook the spaghetti in a large pot of boiling salted water until tender but still firm to the bite, stirring occasionally, about eight minutes. Drain.
2) Toss with the sun-blushed tomatoes. Set aside to cool completely otherwise the hot pasta could curdle the eggs when you add them later on.
3) In a large bowl, whisk the eggs, salt, and pepper, Parmesan, and fontina to blend. Add the cooled spaghetti mixture; toss to coat.
4) Preheat the oven grill. Melt the butter and oil in a 23cm-diameter non-stick frying pan over medium heat. Transfer the spaghetti mixture to the skillet, pressing to form an even layer. Cook until the bottom is golden brown, about three minutes. Transfer the skillet to the grill.
5) Grill until the top is golden brown, about five minutes. Cool in the skillet to room temperature.
6) Invert the torta onto a platter. Cut into wedges and serve at room temperature.