Peer-to-Peer (P2P) energy trading provides various benefits over conventional wholesale energy markets and makes renewable energy more accessible. This paper proposes a novel multi-layer P2P energy trading system for microgrids based on IOTA 2.0, which is a distributed ledger technology (DLT) primarily designed for Internet-of-Things (IoT) applications. The proposed energy trading system, which is a manifestation of a cyber-physical system (CPS), exploits the benefits brought by IOTA's unique ledger structure as well as the recently introduced IOTA smart contract protocol (ISCP). Further, it implements a uniform double-auction market mechanism and a hierarchical routing structure for interconnected microgrids. Performance evaluation demonstrates key benefits over wholesale markets as well as speed, energy efficiency and cost benefits over conventional blockchain-based P2P energy trading systems.