$contentObject = GeneralUtility::makeInstance(ContentObjectRenderer::class);
return $contentObject->cObjGetSingle('CONTENT', array('table' => 'tt_content', 'select.' => array('pidInList'=> 0, 'where' => 'uid=' . $arguments['uid'])));
But this is much easier: brot.krue.ml/render-typo3-content-element-in-fluid-template/