Mix the grapefruit, tomatoes, onion parsley, 1 1/ 2-ounce ginger, oil and vinegar. Season with salt and pepper. Refrigerate until needed.
Remove all the fat from the sirloin and split the meat in half length-wise. Make an incision at one end of the "eye" and with steel, such as a skewer, make a tunnel hole through the meat without breaking the outer meat.
Mix remaining ginger with basil and garlic. Using the scallions as plungers, push the basil mixture with the scallions into the center of the sirloin. Coat the outside of the meat with the five-spice powder.
Roast the sirloin to the desired temperature. Slice the meat into thin even pieces and arrange on a plate beside the grapefruit salad.