Pierce potatoes with fork; place on microwavable paper towel in microwave oven. Microwave on High 8 to 10 minutes, turning after 4 to 5 minutes, until tender. Let stand about 5 minutes until cool enough to handle.
Cut potatoes in half lengthwise. Scoop out about 2 tablespoons of pulp from center of each half; place in medium bowl. Reserve potato shells. Mash potato pulp with fork. Stir in sour cream; set aside.
Meanwhile, in 10-inch skillet, cook beef, salt and pepper over medium-high heat 5 to 7 minutes, stirring frequently, until beef is thoroughly cooked; drain. Stir in corn, tomato sauce, onions and tomato. Cook 3 to 4 minutes, stirring occasionally, until hot and bubbly.
Spoon beef mixture into potato shells. Top each with about 1/4 cup potato and sour cream mixture. Place on microwavable platter. Microwave uncovered on High 4 to 6 minutes or until thoroughly heated. Serve immediately. Top with chives.