Access field data from entity in block plugin
Try this:

public function build() {
  $query = \Drupal::entityQuery('node')
    -&gt;condition('type', 'blog_post');
  $nids = $query-&gt;execute();

  $build = [];
  foreach ($nids as $nid) {
    $node = Node::load($nid);
    $build[] = $node-&gt;blog_summary-&gt;view();
  }
  return $build;
}