Prepare 9x9 inch baking dish with cooking spray
Cook potatoes with skin on in salted water for 30 minutes until fork tender, drain and allow to cool, then peel and dice. Place potatoes in the bottom of the casserole dish
In skillet, melt butter and then saute the onion until tender
Add in Rotel and cubed cheese. Stir constantly until the cheese has melted and everything ic combined well. Pour over potatoes.
Bake for 30 minutes at 350