BEAT first 7 ingredients in medium bowl with mixer until blended.
RESERVE 1 tsp. onions. Add remaining onions, crabmeat and 1/2 cup shredded cheese to cream cheese mixture; mix well. Spoon into microwaveable bowl.
MICROWAVE on HIGH 3 min. or until heated through, stirring after 1-1/2 min. Top with remaining shredded cheese and reserved onions.