Tying into existing cast iron line for bathroom addition

[CatoMaior]

Hello all,

I'm adding a second story bathroom on my house, and need to tie my 3" drain into the existing cast iron line. The previous owner ran a 1.5" pvc drain into one of the cleanouts, which I understand is not to code (see picture). Is there any way to tie into this location with any special fitting that would be to code? If not, I guess I will need to tie in before the cleanout? Any advice would be greatly appreciated.

Thanks!