2 to 3 tablespoons extra-virgin olive oil
½ red onion, thinly sliced
6 large cloves garlic, thinly sliced
2 bunches beets, beets trimmed, peeled, halved, and sliced into ¼-inch-thick half-moons
2 bunches beet greens, stemmed
sea salt
1 tablespoon red wine vinegar
freshly-ground black pepper