Do I pay UAE corporate tax on rental income from my Dubai apartment?

It depends how you hold it. A natural person leasing property in their own name, without a business licence, sits outside UAE corporate tax scope, so that rental income is effectively tax-free. Hold the same property through a company, LLC or SPV and the rent becomes business income taxed at 9% on net profit above AED 375,000. Your home-country tax may still apply.