API call returns some German umlaut characters but are not recongnized by cypress

[khanlendico]

let longListFile = 'Cypress/fixtures/longlist.csv';

cy.request({
            agent: false, pool: { maxSockets: 100 },
            method: 'GET',
            url: <url hidden>
            headers: { 'Content-Type': 'application/json', charset: 'utf8', 'Access-Control-Allow-Origin': 'https://something.de' }
        }).then((response) => {
            const utf8Content = response.body
            cy.writeFile(longListFile, utf8Content, 'utf8');
        })

I'm trying to save the response into a csv file but the German umlauts are converted to something weird like
from "Schönefeld" to "Sch�nefeld".
As I understand, the german characters are included in utf8 encoding. Am I doing something wrong?