Position a rack 4 to 6 inches from the broiler and preheat the broiler. Whisk the eggs, milk and cheese in a large bowl. In another bowl, toss the tomatoes, basil, 1 tablespoon olive oil, 1/2 teaspoon salt, and pepper to taste.
Heat 1 tablespoon olive oil in a large nonstick ovenproof skillet over medium-high heat. Add the scallions, radicchio, sugar, and salt and pepper to taste. Cook, stirring, until the radicchio is tender, about 3 minutes, then add to the bowl with the egg mixture and stir. Wipe out the skillet.
Heat the remaining 1 tablespoon olive oil in the skillet over medium-high heat, tilting to coat the pan. Add the egg mixture and cook, undisturbed, until the bottom starts setting, about 30 seconds. Top with spoonfuls of ricotta; transfer to the broiler and cook until the frittata is set and golden, 3 to 5 minutes. Loosen the edge with a rubber spatula; slide out of the skillet. Cut into wedges. Serve with the tomato salad.
Per serving: Calories: 381; Total Fat: 28 grams; Saturated Fat: 9 grams; Protein: 20grams; Total carbohydrates:11 grams; Sugar: 0 grams; Fiber: 2 grams; Cholesterol: 461 milligrams; Sodium: 558 milligrams