Depending on which species you have, I have a Horsefield and she loves Cabbage! It's advised you give Cabbage more than romain lettuce as that's full of water, isn't great for their diet!
They can, but not as part of a daily diet. I have had mine for a year and have fed cabbage 3-4 times. Not saying its what you should do. I like to follow what the tortoise table mentions.