Wash the beets well, scrubbing the skins since they can be quite dirty even though we remove the peel later.
Lay a sheet of foil on a baking tray and place a sheet of parchment paper on top. (This keeps the foil from touching the beets.)
Place the beets on the tray and roast in a 400°F oven for about 1 hour, sometimes up to 1½ hours, until a knife slides in easily.
Let them cool slightly, then peel using your hands, a knife, or even under running water. The skins come right off.
Slice or chop the beets however you like and place them in a bowl.
Add the diced red onion and chopped parsley.
Add the minced garlic, olive oil, vinegar, lemon juice, salt, and black pepper.
Toss gently and taste for seasoning.