Decorative cabbage and kale are not generally consumed.One they taste like crap, two commercial grown ornamentals are heavily fertilized and sprayed with a slew of pesticides and fungicides.I spent nearly 20 years in the decorative/landscape plant business, I personally would not eat it. But that just my opinion.
That really looks like a over grown red cabbage.
Might be a bit hard but usually it´s used in salads, coleslaw and in pickled form.
Good stuff with a smelly side effect