This recipe describes a computational framework for conducting a multi-hazard risk assessment of a building portfolio subjected to megathrust subduction earthquakes and tsunamis. The simulation-based framework implements time-dependent earthquake occurrence models and characterises uncertain earthquake rupture models with variable fault geometry and heterogeneous slip distribution. Integrating earthquake-tsunami hazard models with an exposure model for the built environment and seismic and tsunami fragility functions enables quantitative risk assessment. The final outputs from the developed tool include single-hazard and multi-hazard loss exceedance probability curves and related risk metrics.