I had this issue from kiteboarding way too much. The wrist extension exercises really focused on the damaged area and after a couple of months all better. The guidance I used (not this page but similar) said to gradually increase the weight used. I found the third exercise on this page the most helpful. The trick is to strengthen the tendon is to let the weight back down slowly, you want resistance as the connective tissue is lengthened. I ended up using an 8-lb dumbell.
Exercises for Tennis Elbow: 5 Moves for Rehab
Tennis elbow is caused by inflammation of the muscles of the forearm that attach to the elbow. It’s typically an overuse injury triggered by repetitive activity. If you’ve had tennis elbow in the past or are just recovering from it, these five exercises can help you strengthen your forearm...
www.healthline.com