Drain canned beets and place them in a large quart sized mason jar or medium bowl.
Add the onion, vinegar, sugar, olive oil, black pepper, and enough water to cover beets (I found that 1/2 cup was enough for my quart mason jar).
Allow beets to sit for at least 30 minutes before eating, but preferably overnight.
Notes
Recipe NotesThis recipe calls for canned beets, but if you make homemade steamed or cooked beets, then add about 3 cups of sliced beets + 1/4 teaspoon salt to this recipe instead of canned.