Yoga in general and deadlifts are what I do. Back extension in both directions laying on your belly on a bench is good for strengthening it safely, start with small range of motion and extend it as you can.
Remember a few things - we spend more time bent forward than back, so make sure to strengthen the back in the arched direction as well. The whole body is connected so develop it in a balanced way. And move in every direction (intentionally). That last one is what yoga is so good for.
Yeah boobs are luck or money. Ass and legs are accomplishments!