Place an even layer of sliced onions onto the base of the MicroPro® Grill. Place cover on onions in the grilling position. Microwave on high power 7 minutes. Remove from microwave and stir onions. Replace cover and microwave on high power an additional 7 minutes or until caramelized.
Transfer onions to the base of the PowerChef® System fitted with blade attachment. Let stand 10 minutes. Cover and pull cord until onions are well minced.
Replace blade attachment with paddle attachment. Add sour cream, salt, cream, vinegar, garlic powder and mayonnaise. Cover and pull cord until well blended.
Remove paddle from PowerChef®. Cover and refrigerate at least 10 minutes, up to overnight. Serve cold as a dip with vegetables, chips, or pita wedges, or serve as a sauce for steak, chicken, or fish.