I presume Mattito's has affiliation with Matt's El Rancho and Matt's Rancho Martinez. I've not heard of this particular restaurant, though.
The recipe is in Matt Martinez's cookbook. I don't own a copy, but I know it's there. But, yeah, the above ingredients are accurate. At least at Rancho Martinez in Dallas, they throw in a scoop of sour cream which, if I understand the story, was in the original incarnation of the dish Matt prepared for Bob Armstrong in Austin all those years ago. I have never known the Austin restaurant to add sour cream, though.
Do not post commercial recipes without permission of the copyright owner. If someone wants to ask Matt's El Rancho if it is ok to post their recipe here and they approve, I'll be happy to allow it.