Frittata with Peppers and Onions with Roasted Cherry Tomato Sauce

Name: Frittata with Peppers and Onions with Roasted Cherry Tomato Sauce
Ingredients: 2 tablespoons butter; 1 red bell pepper, seeded and thinly sliced; 1 yellow bell pepper, seeded and thinly sliced; 1 medium Spanish onion, halved and thinly sliced; Salt and freshly ground black pepper; 14 large eggs; 1/3 cup grated Parmigiano-Reggiano cheese; 1 tablespoon finely chopped fresh oregano; 1/4 cup chopped fresh flat-leaf parsley; Roasted Cherry Tomato Sauce, recipe follows; Fresh basil, to garnish; 3 tablespoons olive oil; 1 pint cherry tomatoes, cut into quarters; 2 cloves garlic, made into a paste with salt; 1/4 cup chopped fresh basil, coarsely chopped