It's been translated too literally. It means roast turkey or turkey cutlet.
"I eat a turkey steak" is wrong, but "I eat turkey steak" is correct. Why not both?
In the UK the word "steak" sometimes means food that is shaped into a steak shape to be cooked, so turkey steak, fish steak or (god help us !) cauliflower steaks www.standard.co.uk/lifestyle/foodanddrink/how-to-make-cauliflower-steak-ms-a3736626.html