Preheat oven to 400°. Spread Tater Tots evenly in an ungreased 13x9-in. baking dish. Bake, uncovered, 10 minutes.
Meanwhile, in a large skillet, cook and crumble beef over medium heat until no longer pink, 5-7 minutes; drain. Stir in seasonings, soup, milk, broccoli, 3/4 cup onions, 1/2 cup cheese and tomato; heat through. Pour over potatoes.
Bake, covered, 20 minutes. Sprinkle with the remaining onions and cheese. Bake, uncovered, until cheese is melted, 5-10 minutes.