UpperTorso not facing the part?

So, I'm trying to make the UpperTorso of my character face the humanoidRootPart of another player, only problem being i suck at math.

I honestly don't see what's wrong with this code If anyone could explain to me how to do it i would be really thankful.

while wait() do
    local char = script.Parent
    local hrp = char.HumanoidRootPart
    local waist = char.UpperTorso.Waist

    local space = math.atan2(hrp.Position.Y, target.PrimaryPart.Position.X)

    print(space)

    waist.C0 = waist.C0:Lerp(CFrame.fromEulerAnglesXYZ(0, math.rad(space), 0), 0.1)
end

As you can see, it assigns the cframe just fine, but it doesnt want to turn the UpperTorso? Please help if you can.