Place the halved potatoes and carrot pieces in a large pot and cover with cold water by about 1 inch. Stir in ¾ tsp salt. Bring to a gentle boil over medium-high heat.

After 10 minutes of boiling, carefully add the eggs to the pot. Continue cooking until potatoes and carrots are tender when pierced, 15–20 minutes total.

Drain the pot. Transfer potatoes, carrots, and eggs to a tray to cool until comfortable to handle.

While they cool, combine the chopped red onion, apple cider vinegar, and a pinch of salt and black pepper in a small bowl. Let sit to mellow.

Peel the eggs. Cut cooled potatoes, carrots, and eggs into small bite-size cubes; place in a large mixing bowl.

Add peas, corn, and the marinated onions along with their vinegar to the bowl.

Fold in the mayonnaise until everything is evenly coated and creamy.

Taste and adjust with more salt and pepper if needed.

Choose your style: For Ensalada Rusa, gently fold in the well-drained sliced beets last. For ensalada mixta, skip the beets.

Cover and refrigerate at least 1 hour (up to 3 days) before serving for best flavor and texture.