Trim any roots off the greens and rinse very well. Fill a large stockpot with water and bring to a boil (I used an 8-quart stockpot and filled it with 5 and a half quarts of water).
When the water comes to a boil, add a generous pinch of salt and the greens. Submerge them completely and cook until the stems are soft and fork-tender; this can take anywhere from 10-20 minutes, depending on the thickness of the stems.
Drain the greens and dress with the olive oil, lemon juice, and salt to taste. If making ahead, refrigerate the greens after draining and save the dressing just before serving.
This can be served warm or at room temperature.