How to send data to raw CUPS printing queue?

I am using Xamarain.Mac (with gtk#) and I need to send raw ZPL commands to CUPS printer. Raw commands look like text. They are not "images". I see that Mono can print images via System.Drawing, but how can I send raw data (raw text) ?

Basically I need an equivalent of what TextWriter on Mac does or equivalent of the following command: lpr -P "Zebra" label_raw.txt

Any piece of sample code would help.

Thank you