DensityPlot[Cos[2π (Sqrt[(x^2)+(y^2)+(z^2)])](((x^2)+(y^2))/((x^2)+(y^2)+(z^2)))/.{y->0},{x,-2,2},{z,-2,2},PlotLegends->Automatic,PlotPoints->100]

DensityPlot[(((x^2)+(y^2))/((x^2)+(y^2)+(z^2)))/.{y->0},{x,-2,2},{z,-2,2},PlotLegends->Automatic,PlotPoints->100]