Both, because these are two words that share one spelling. The verb resume, to start again, goes back to the Latin resumere, to take back. It is said rih-ZOOM, or rih-ZYOOM in British English, with the stress at the end.
The noun is the French word résumé, meaning summarized. It keeps a French-style ending, may, and puts the stress at the front: REZ-uh-may. The accents in résumé show which word it is, but many people leave them out.
In American English, a resume is the document you send with a job application. British English usually calls that a CV and uses résumé for a summary. Let the meaning decide: a document is REZ-uh-may, an action is rih-ZOOM.