For the past few years I've considered Russian food to be the traditional Petrov Day food for my own celebrations, but I've never managed to write a post about it at a reasonable time. Today, a few weeks before Petrov Day, I managed to think about it at a reasonable time and figured I'd rather do an 80/20 post about it, and hope people contribute more in the comments. 

Why Russian Food?

• It's good for celebrations to have specific food, such as turkey for Thanksgiving. They feel more special that way. 
  • Most people don't eat Russian food on a regular basis, so it can be a "special" thing, in a way that e.g. hamburgers wouldn't be.
• The biggest Petrov Day stories (Petrov and Arkhipov) are about Soviets during the Cold War, so it's thematic.
• Many rationalists, such as myself, are of Russian / Eastern European descent so already have holiday memories around Russian food.

Easy Mostly Veg*an Russian Foods

• Kvas, a beverage with tastes in between soda and beer, very lightly alcoholic, and available at your local Eastern European store.
• Kasha aka buckwheat. Very easy to make. If you are a veg*n there are good fake chik'n bouillons available, and I strongly recommend cooking this with chicken / chik'n broth instead of plain water. Mushrooms and onions only if you're feeling fancy.
• Veg*an Sausage. It's just a good easy veg*n protein option, and sausage is often paired with kasha.
• Borscht, a vegetable soup with beets and cabbage, topped with (optional) sour cream. For an easy version, search for a recipe that uses canned beets. I'll put my dad's easy recipe in a comment below.
• Black bread with butter and (optional) salmon roe.
• Russian chocolates, individually wrapped. Available at your local Eastern European store. The Mishas (little bear) and chocolate covered jellies are generally well-liked.