Preheat oven to 375. Coat a 9 x 13 inch baking dish with nonstick spray.
For pasta, cook cavatappi in large pot of boiling salted water til slightly soft, 5 minutes; drain and rinse with water.
For sauce, melt 4 Tbsp. butter in large pan over medium heat. Add scallions; cook 1 minute. Whisk in flour and paprika and cook 2 minutes. Whisk in milk and bring to a boil; cook til thick, 1 to 2 minutes, reduce heat to medium low and whisk in cheeses, Dijon and Worcestershire. Simmer til cheese melt, about 2 minutes.
Stir in tomato and season with Tabasco and salt. Transfer sauce to large bowl and stir in cavatappi. Transfer to prepared dish.
For topping, mix panko and 3 Tbsp. butter, then sprinkle over mac 'n cheese. Bake mac 'n cheese til bubbly and topping is golden brown, 30 to 35 minutes. Let rest 5 minutes before serving.