🤔 Avataṃsaka?

Tibetan sources allude to “rNa rgyan gyi gtsug lag khang” in Kashmir (mKhyen dbang gsung rtsom, p. 220). Also the Shes bya mdzod refers to the name. But what would be the Sanskrit original of the name (if it indeed existed)? Perhaps Karṇapūra? Avataṃsaka? Was there indeed such a temple in Kashmir?