Let me begin by saying that I grew up in SoCal and have traveled extensively throughout the southwest and had my fill of Mexican food, looking for the good stuff. The two dishes I look for are tamals and chile rellenos: both specialty dishes that require careful attention to detail, and both of which can be done badly.
Dona Maria's had the BEST tamals AND chile rellenos I have ever had. First, the tamals: most places have a thin layer of meat wrapped in corn meal. Here, you have a rather sizable portion of meat wrapped in a thin layer of corn meal.
Next, the chile rellenos. If you don't do them right, you have a gloppy, oil-soaked eggy mess. Dona Maria's were done perfectly: crispy and filling.