Select saute or browning setting on a 6-qt. electric pressure cooker and adjust for medium heat; add oil. Brown ribs in batches, adding additional oil as needed. Remove ribs. Brown onions. Add ribs back to the pressure cooker. Add water. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 40 minutes. Let pressure release naturally for 10 minutes, then quick-release any remaining pressure., In a small saucepan, combine the remaining ingredients; cook and stir over medium heat until heated through. Remove ribs from pressure cooker; discard cooking juices. Return ribs to pressure cooker. Pour sauce over top. Lock lid; close pressure-release valve. Adjust to pressure-cook on low for 5 minutes. Allow pressure to naturally release for 5 minutes and then quick-release any remaining pressure. Serve ribs with sauce.