Error: Class ‘DOMDocument’ not found

Hello, I am getting the following error when I try to manually download or publish an article via the plugin.

Fatal error: Uncaught Error: Class 'DOMDocument' not found in /var/www/html/wp-content/plugins/publish-to-apple-news/includes/apple-exporter/class-exporter-content.php:228 

Stack trace: 
#0 /var/www/html/wp-content/plugins/publish-to-apple-news/includes/apple-exporter/builders/class-builder.php(123): Apple_Exporter\Exporter_Content->nodes() 
#1 /var/www/html/wp-content/plugins/publish-to-apple-news/includes/apple-exporter/builders/class-components.php(793): Apple_Exporter\Builders\Builder->content_nodes() 
#2 /var/www/html/wp-content/plugins/publish-to-apple-news/includes/apple-exporter/builders/class-components.php(42): Apple_Exporter\Builders\Components->split_into_components() 
#3 /var/www/html/wp-content/plugins/publish-to-apple-news/includes/apple-exporter/builders/class-builder.php(66): Apple_Exporter\Builders\Components->build() 
#4 /var/www/html/wp-content/plugins/publish-to-apple-news/includes/apple-exporter/class-exporter.php(216): Apple_Exporter\Builders\Builder->to_array() 
#5 /var/www/html/wp-content/plugins/publish in /var/www/html/wp-content/plugins/publish-to-apple-news/includes/apple-exporter/class-exporter-content.php on line 228

There has been a critical error on your website. Please check your site admin email inbox for instructions.

Any suggestions for what I can do to alleviate this.