Cut the potatoes into thick pieces. Place them in a medium saucepan, add enough water to cover them.
Cook over medium-high heat until potatoes are tender, about 15 minutes. Drain and prepare the puree in the same saucepan.
Preheat the oven to 350F. Add in a saucepan, cream cheese, BBQ sauce and sour cream. Beat by hand with wire whisk until well blended; add onion salt, garlic salt, and pepper.
Spoon the mashed potatoes into a baking dish. Sprinkle it with cheddar cheese. Bake for 20 minutes.
Arrange tomato slices on top, sprinkle with chives. Bake for 5 minutes. Serve hot.
