Place beets, potatoes, and carrots in separate pots with cold salted water. Cook beets for 45-60 minutes, potatoes and carrots for 25-35 minutes, until fork-tender. Cook beets separately to prevent coloring other vegetables.

Hard-boil eggs for 10 minutes, then plunge into ice water. Drain all vegetables and let cool completely to prevent soggy salad and color bleeding.

Peel all cooled vegetables and eggs, then dice everything into uniform 1/4-inch cubes. Handle beets last and consider wearing gloves to avoid staining.

In a large bowl, combine diced potatoes, carrots, eggs, sauerkraut, pickles, onion, and peas first. Mix thoroughly, then add beets last to prevent overpowering other colors.

Whisk together sunflower oil and vinegar, then drizzle over salad. Season with salt and pepper. Fold gently with large spoon. Let rest for at least 30 minutes before serving.