Heat Oven To 350 Degrees F. Brown Meat In Large Skillet; Drain. Return Meat To Skillet. Add Tomatoes, Water And Seasoning Mix; Stir. Cook 10 Minute, Stirring Occasionally. Stir In 1/4 Cup Sour Cream. Place Half The Chips In 13X9-Inch Baking Dish; Cover With Layers Of Half Each Of The Meat Mixture And Cheese. Repeat Layers. Bake 20 Minute Or Until Heated Through. Top With Onions And Remaining Sour Cream.