Preheat oven to 425°F (246°C). Melt butter in 2-quart (1.9 L) saucepot over medium heat. Add onion and salt and cook 3 minutes or until softened. Add flour and garlic and cook 2 minutes, stirring constantly.
Gradually stir in milk and bring to a boil over medium-high heat. Reduce heat to low and simmer 3 minutes, stirring frequently, until mixture is thickened. Add 1 ½ cups (355 mL) cheese and stir until melted.
Arrange pasta to 2-quart (1.9 L) baking dish. Pour sauce over pasta and stir gently until evenly coated. Evenly top with remaining cheese and Green Giant* Veggie Tots.
Bake 25 minutes or until mixture is bubbling and Green Giant* Veggie Tots are golden brown.