This might be close to what you want, they aren't exactly concentric,
more like stacked:
box  {< -5, -5,  0>, < 5, 5, 5 >
 texture {
  pigment {
   function {sqrt(x^2 + z^2)-y}
   color_map {
    [0 color Black]
    [1 color White]
   }
  }
 }
}

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