These logos are about 3x wider than they are tall, and are designed to be unobstrusive and out of the way so that the reader has more space for what they actually care about: your content and navigation.
See rethinking the newsletter for examples of industry-leading content sites who've designed their logos for a mobile-first, user-first world.
Modern Menu logo
Under Admin > Feast Plugin > Settings you'll find an option to add a modern logo:
There are two images that must be specified - a 200x70 size and a 400x140 size (called a "retina image").
We no longer recommend using the theme's implementation of the logo.
The (outdated) logo setup built into the themes was designed at a time when recipe content sites were food blogs and were self-serving and creative expressions of the owners ego.
Your readers get zero value from your logo and the days of monstrous, oversized logos are gone.
If you still want to pursue this, you can upload your logo at the size you want it to display at to Customize > Header Image:
The Feast Plugin also contains an enhancement to upload a retina quality version of the theme logo in Admin > Feast Plugin > Settings:
Theme logo CLS
The theme's menu doesn't include a height/width attribute by default, in order to support displaying any size logo. You can add the image width/height attribute by using WP Rocket's "Add missing image dimensions" setting under Admin > Settings > WP Rocket > Media
Creating a logo
For future proofing, we'd recommending creating the image at 800x280, and saving two scaled version (400x140, 200x70) for use on your site. That way, if there's ever a need for a larger size in the future, you have some wiggle room.