Put the beets in a medium saucepan and cover with water. Put over high heat and bring into a boil. Lower the heat to medium and cook for 15-20 minutes.
Preheat the oven to 400°F/200°C. Drain the beets and wrap them in aluminum foil. Bake them for 20-25 minute or until they're tender (depends on their size).
Let them cool down then peel them. Using a Japanese mandoline or sharp knife slice them thin (not too thin though).
Arrange the slices, in one layer, on a large plate. Drizzle olive oil and squeeze the lemon over, season with sumac and salt, then garnish with fresh oregano leaves. Serve or cover with plastic wrap and store in the fridge until you ready to eat it.
You can use any color of beets. Try to find medium or small beets. The bigger they are the longer to cook
If you don't have sumac put white pepper or black pepper instead
It's extra delicious with crushed toasted almonds or hazelnuts
Use any herb such parsley, basil or dill, chopped
If you don't have lemon juice use 1 teaspoons apple cider vinegar