Preparation Combine cranberries, onion, sugar and salt in processor. Chop coarsely, using on/off turns. Transfer mixture to medium bowl. Mix in sour cream and horseradish. Season to taste with salt and pepper. Refrigerate until chilled, about 1 hour. (Can be prepared 1 day ahead. Cover and keep refrigerated.)
Preparation Combine cranberries, onion, sugar and salt in processor. Chop coarsely, using on/off turns. Transfer mixture to medium bowl. Mix in sour cream and horseradish. Season to taste with salt and pepper. Refrigerate until chilled, about 1 hour. (Can be prepared 1 day ahead. Cover and keep refrigerated.)