For the sauce: In a skillet, cook sausages according to package directions; cool. Cut sausage into 1 inch pieces. In the same skillet, melt butter, saute onion and garlic until transparent. Add peppers. Continue to cook 5 minutes. Stir in tomatoes, basil, sugar and salt. Bring to a boil; reduce heat, add sausage. Simmer until excess liquid is reduced by half. The sauce can be prepared in advance, store in refrigerator and reheated. For the frittata: in a mixing bowl, whisk eggs, sour cream, basil, salt and pepper In a 10 inch nonstick ovenproof skillet, saute onion for 1 minute. Pour egg mixture into skillet. Cook over Medium heat until eggs are set and light brown on bottom, about 8-10 minutes. Remove from heat. Sprinkle with cheese.

Preheat broiler; place skillet 6 inches from heat for 2 minutes or until cheese melts. Serve immediately with sauce. Serves 8-10.