foo.php

NodeType::create(['name' => 'Ponies', 'type' => 'ponies'])->save();
    $uid_field = $this->entityManager->getBaseFieldDefinitions('node')['uid'];
    $uid_field->getConfig('ponies')->save();
    /** @var \Drupal\node\NodeInterface $node */
    $node = Node::create(['type' => 'ponies']);
    $owner = $node->getOwner();