You need a visa for Cameroon if you have a Spanish passport
Visa options for Cameroon
Electronic visitor visa
Travelers need a visa to visit Cameroon for Business or Tourism. A Cameroon eVisa is the fastest and easiest way of obtaining a visa for Cameroon because travelers can submit their applications and supporting documents online. Once the application is approved, travelers receive their eVisa confirmation electronically. Travelers with an eVisa issued online shall receive either at the Border Post of Entry or at the competent Diplomatic Mission or Consular Post for applicants having completed their biometric enrolment at said Mission or Post. This phase is completed with the printing of the visa sticker on the applicant's passport. Travelers residing near a diplomatic mission of Cameroon may be required to provide biometrics in person before visa issuance.
This is not offered by sherpa°.
Apply on the government site.