Yes — that is exactly what this route is for. What you may do on the Spanish side depends on which of the two scenarios applies to you:
- Employment relationship (actividad laboral): in Spain you may work only for the company based outside the national territory for which you telework. There is no 20% allowance here — working for a company located in Spain is not permitted.
- Professional relationship (actividad profesional): you keep the professional relationship with the company you applied with. You may also work for a company located in Spain, as long as that engagement is a professional relationship (never employment) and does not exceed 20% of your total professional activity.
Note that the 20% cap measures your total professional activity, not your income, and it applies only to the self-employed professional route. In every case the work must be performed remotely through computer, telematic and telecommunication means, not from a Spanish office. Most Turkish remote employees simply keep working for their Turkish employer and take on no Spanish-side work at all.