Sprinkle pork with 3/4 teaspoon salt and pepper. Heat oil in a large nonstick skillet over medium-high heat. Add pork; cook 6 minutes, browning on all sides. Remove pork from the pan. Add onion to pan; reduce heat, and cook for 8 minutes or until browned. Remove onion from pan; sprinkle with remaining 1/4 teaspoon salt, and set aside. Add beer to pan; cook 1 minute over high heat or until reduced to 1/2 cup.
Return pork and onion to pan; add broth, and bring to a boil. Cover, reduce heat, and simmer 30 minutes. Stir in cranberries; cover and cook 30 minutes or until pork is tender. Remove from heat. Place pork on a cutting board; cover and let stand 5 minutes. Cut each tenderloin into 12 slices. Serve with onion mixture.