1In blender, place plums and lemonade concentrate. Cover and blend on medium speed until smooth; set aside.
2In 2-quart saucepan, melt butter over medium heat. Cook onion in butter about 2 minutes, stirring occasionally, until tender. Stir plum mixture and remaining ingredients into onions. Heat to boiling; reduce heat. Simmer uncovered 15 minutes, stirring occasionally.
3Set oven control to broil. Grease broiler pan (without rack). Place venison steaks in broiler pan. Spoon 1/2 cup of the plum sauce evenly over venison.
4Broil venison with tops about 4 inches from heat about 10 minutes or until light brown. Turn venison; spoon 1/2 cup of the plum sauce evenly over venison. Broil about 5 minutes longer or until rare to medium-rare doneness. Heat remaining sauce; serve with venison.