Upside-Down Sheperd's Pie

This recipe was in an email I got recently from Kraft. It looked cheap and easy and used beef, which I always struggle to find recipes for. It was cheap and it was easy and it was pretty good too! The Italian dressing wasn't overpowering, but did give it a more jazzy flavor.

3/4 lb. new potatoes (I used red potatoes)
1/2 cup water
1/4 cup Italian Dressing
1 lb. extra lean ground beef (I used 1/2 lb.)
1 onion, chopped (I used 1/2)
1 cup frozen corn
1 tomato, chopped
1/3 cup Shredded Italian Cheese Blend (I just used cheddar)

-Heat oven to 400ºF. Microwave potatoes and water in 2-qt. microwaveable ovenproof casserole on HIGH 10 to 12 min. or until potatoes are tender. Let stand 5 min. (I boiled my potatoes like normal and used milk to make creamy)
-Meanwhile, heat dressing in nonstick skillet on medium-high heat. Add meat and onions; cook and stir until meat is browned.
-Stir in corn and tomatoes.
-Drain potatoes; return to dish. Flatten with bottom of small cup or bowl; top with meat mixture and cheese. Cover.
-Bake 25 min. or until casserole is heated through and top is golden brown, removing lid after 20 min.