Step 1Cook potatoes in salted water to cover until just barely tender, about 15 minutes for small potatoes, longer for larger potatoes. Drain; spread on paper towels to cool. Cut into quarters or sixths for large potatoes; peel, if desired (peeling is not necessary).
Step 2Put olive oil in 13x9-inch baking pan. Heat at 400 degrees 5 minutes. Add potatoes in single layer. Sprinkle with 1/2 teaspoon salt. Roast until lightly browned, shaking pan occasionally to turn potatoes, about 45 minutes. Transfer to large bowl.
Step 3Add tomato, onion, red wine and balsamic vinegars, capers, garlic and red pepper flakes. Toss to mix. Let cool to room temperature. (Can be served immediately or chilled overnight. If chilled, let come to room temperature before serving.) To serve, toss, add sliced basil leaves and adjust seasoning. Garnish with basil leaves.