2 to 3 medium to large red beets, trimmed and brushed clean
1/2 pound pole beans, trimmed and cut into 1-inch pieces
1 large red onion, peeled, halved, and thinly sliced
1/4 cup white or red wine vinegar
1/3 cup olive oil
Kosher salt and black pepper to taste
1 to 2 sprigs of thyme, leaves only (optional)
Bring a large pot of water to a boil over high heat. Add the beets and cook until tender, about 1 hour. (Reserve the cooking liquid, strain it, and drink it!). Peel and halve each beet. Cut each half into 1/4-inch thick wedges.
In the meantime, put the sliced onion in a large bowl and add the vinegar, oil, and salt and pepper to taste. Toss well to coat the pieces evenly. Let stand at room temperature for at least 1 hour, tossing every 15 minutes or so to redistribute the dressing and onions.
Bring a small to medium pot of salted water to a boil over high heat. Add the pole beans and cook until tender, 5 to 10 minutes. Drain and shock until cold running water.
In a large serving bowl, toss together the beets and pole beans. Adjust seasoning with salt and pepper to taste. Add the onions on top, garnish with thyme (if using) and serve.
NOTE: This recipe can be made a day ahead of time. While it is really good when freshly made, it tastes even better the next day.