\starttext
  % By TeX

  \centerline{
    \starttable[|c|]
      \HL
      \VL 5 \VL\AR
      \HL
    \stoptable
  }

  % By Lua

  \startluacode
    context([[\centerline{]])
      context.starttable{"|c|"}
        context.HL()
        context.VL(5); context.VL(); context.AR()
        context.HL()
      context.stoptable()
    context([[}]])
  \stopluacode
\stoptext