With the speed rise of heterogeneous Blockchain (BC) platforms, interoperability became a critical area of research barrer for a variety of use cases, ranging from supply chain to healthcare. Consequently, a number of BC interoperability solutions were proposed to overcome these issues. One of these is Bifröst, a notary-based BC interoperability Application Programming Interface (API) which enables users or existing applications to interact seamlessly with multiple BCs. An early prototype of Bifröst was built, which proved its feasibility, nonetheless, it failed to allow interactions with Smart Contracts (SCs) across BCs. In this context, we present in this paper an extension of Bifröst architecture enabling secure cross-BC SCs using the Trusted Execution Environment (TEE). The proposed architecture is also fault tolerant by means of a logging module that facilitates the recovery of partially completed transactions in case of a crash.