For the beef: Preheat the oven to 375 degrees F. Roast the meat 15 minutes in a roasting pan. Remove, and cool. Thinly slice with a sharp knife. Mix the oil, lemon zest and juice, and basil in a bowl. Toss with the meat in a glass casserole. Season the mixture with salt, and pepper, and spread the mixture out, cover, and refrigerate all day or overnight, turning once or twice. Serve at room temperature. For the potatoes: Bring a large pot of water to the boil. Salt it, as you would for pasta. Add the potatoes, and cook until tender when you test them with a fork. Drain. Toss the potatoes in olive oil, and season with salt and pepper, and serve. For the plate: Plate some beef and potatoes side by side on a plate and enjoy!