1. Preheat oven to 425°F. Line a baking sheet with foil. Pierce potatoes all over with a fork and place on a microwavable plate. Microwave on high until tender, 12 to 14 minutes, turning once. Let cool slightly.
2. In a large skillet over medium-high heat, cook bacon, turning, until crisp, about 8 minutes. Transfer to a paper towel-lined plate to drain. When cool enough to handle, crumble bacon.
3. Cut a thin slice off top of each potato and discard. Spoon insides of each potato into a bowl. Stir in 3/4 of cheese plus sour cream, chives, bacon and tomatoes. Season with salt. Spoon into potato skins (filling will mound up very high). Place on baking sheet, sprinkle tops of potatoes with remaining 1/4 of Cheddar and bake until cheese is golden brown and bubbling, about 10 minutes.