A heat exchange cell for use in a recuperator includes top and bottom plates spaced apart to define therebetween an internal space. Within the internal space are inlet and outlet header tubes communicating with a plurality of internal matrix fins. The header tubes are rigidly affixed to at least one adjacent header tube and to the top and bottom plates. The header tubes may have a rectangular cross-section and may, for example, be metallurgically bonded to the top and bottom plates and to each other through brazing. Rigidly affixing the header tubes to each other reduces the stress on the fillets that bond the tubes to the top and bottom plates. This in turn permits less structural material to be used in the header portions of the cell and reduces pressure drop across the headers.