A supersonic combustion ramjet, or scramjet, emerges as a prospective propulsion solution for air-breathing hypersonic vehicles. Despite its potential, achieving stable supersonic combustion poses significant engineering challenges attributed to the complicated nature of high-speed internal flow, which encompasses phenomena such as shock waves, turbulence, flow separation, and combustion intricacies. \cite{Urzay,Liu} To improve the understanding to the supersonic combustion, direct numerical simulations are employed to analyse supersonic lean premixed hydrogen/air combustion stabilised by a cavity flame-holder within a model scramjet combustor operating at Mach 1.5. The study places particular emphasis on the influence of the inflow boundary layer on both flame structure and combustion characteristics. This is achieved by conducting simulations for three distinct cases: one with fully developed turbulent inflow and two with laminar boundary layers with different thicknesses. The results reveal that the distribution of inflow turbulence vortices homogenously affects the cavity shear layer, resulting in a deep penetration of fresh mixture into the reaction zone. Analysis of flame structure indicates the width of the oxidation region exhibits variations contingent upon the evolution of vortices and flame is stabilised in the product side with the presence of inflow turbulence. Further examination of flame stretch offers insights into turbulence-flame interaction in supersonic flows. The findings indicate similarities with prior studies for the case with turbulent inflow, emphasising the significant impact of vortex development on tangential strain rate. In contrast, the laminar case with a thin boundary layer exhibits a distinctive flame-vortex interaction behaviour, strongly influenced by the impingement of the reactive shear layer onto the cavity aft wall.