How to rotate a part to face a brick?

Alright, I already know how to do it, but I have a weird issue when I rotate the brick to face the part in question. The video of the problem is here: https://youtu.be/dgF7W9D8kEY The problem is that the part I want to turn moves off the base of the turret which looks really bad. How could I fix it? The script is as follows:

function FindClosestPerson()
	for _,v in pairs(game.Players:GetChildren()) do
		if v.Character:FindFirstChild("Torso") ~= nil and v.Character:FindFirstChild("Humanoid") ~= nil and v.Character.Humanoid.Health > 0 then
			if (v.Character.Torso.Position - script.Parent.Union.Position).magnitude <= 20 then
				if v:GetRankInGroup(2874380) < 255 then
				return v.Character.Torso
		end
			else
				return nil
	end 
	end
	end
	end



function NoTarget()
	script.Parent:SetPrimaryPartCFrame(script.Parent.Part.CFrame * CFrame.fromEulerAnglesXYZ(0,0.01,0))
end

function Aim(TargetTorso)
    script.Parent.Union.CFrame = CFrame.new(script.Parent.Union.CFrame.p,TargetTorso.CFrame.p)
end

while true do
	local TargetTorso = FindClosestPerson()
	wait()
	print(TargetTorso)
	if TargetTorso == nil then NoTarget()
	else
		Aim(TargetTorso)
	end
	end

Make the thing you want to rotate a model, and place a invisible part at the bottom. The turret will rotate on the center of this part. Now go to the model's properties, and find PrimaryPart. Set this to the invisible part on the bottom of your model. Now here's what I use to rotate models, it's not my scripting, forgive me if it's not efficient:

local model = workspace.model --The model of the turret
model:SetPrimaryPartCFrame(model:GetPrimaryPartCFrame() * CFrame.Angles(0, math.rad(45), 0)) -- This rotates the model 45 degress

Accept if this helped