Great question — answering as the UphillTech team:
You would need to experiment; but I would start with a 1:1 ratio of liquid to orzo. I would cover the dish with aluminium foil to keep as much moisture in. Remember that the cherry tomatoes will also release some moisture. look at the dish from time to time, if it's not cooked and missing liquid, add some more; if it's cooked and there's too much liquid, quit the cooking and next time use less liquid. You can always add more liquid, but never remove some.
Full answer by Max: https://cooking.stackexchange.com/a/116877 (CC BY-SA 4.0).
Need it done for your business? UphillTech.