In a 4-quart Dutch oven melt butter over medium heat. Add onion, garlic, and salt. Cook 5 minutes or until tender, stirring occasionally. Add potatoes, broth, and dried marjoram. Bring to boiling. Reduce heat. Simmer, uncovered, 20 minutes or until tender, stirring occasionally. Using an immersion blender, puree until smooth. Stir in pomegranate juice. Top each serving with sour cream and fresh marjoram.