In a large sauce pan, cook the beets with salt and water for 60-90 minutes on medium heat, covered. Once cooked, remove from the heat and set aside.
Once cooled, peel the beets and dice them into small 1/2 inch pieces. Alternatively, you can grate the beets.
Toss the beets with red wine vinegar and set aside.
Place the yogurt in a serving bowl and gently blend the beets into the yogurt. I prefer my yogurt to remain mostly white with bright red beet pieces, so I am careful not to over mix.
Garnish the yogurt with mint leaves and nigella seeds.
Serve with Persian flat breads.
Notes
Adjust the tartness by adding more vinegar or if you prefer a touch of sweetness, add a small amount of sugar to the beets.