We were devastated that we only discovered Catedral on our last evening in Oaxaca -- otherwise we would have gone there every night. Having heard that Oaxaca had the best cuisine in Mexico, we'd been disappointed so far. But Catedral was a revelation.
It's in a beautifully restored old mansion, with a lovely indoor patio. Nothing folkloric here: the colours are deep and dramatic, and the ambience is stylish and sophisticated. As was the service. The food was outstanding; this is a long-established family-run restaurant which apparently bases its menu around dishes which the owner's mother refined from traditional Oaxacan recipes. It's very polished, and a different world from most of the "typical Mexican" tourist restaurants in town. A must if you're in Oaxaca...and don't leave it till your last day.