In a cast iron skillet or Dutch oven, making sure the vessel has a lid that fits, warm the olive oil over medium heat.
Saute the peeled, diced onions for at least 5 minutes or until translucent.
Add the peeled, diced carrots and saute for another 5 minutes or so.
Add the clean, chopped collard greens on top of the carrots and onions. It is okay if they are still wet. You may need to carefully press the greens down into the skillet.
Sprinkle the top of the greens with salt, then cover with the lid.
Allow the greens to sweat for several minutes.
Carefully lift the lid and stir the collards. You will see the collards beginning to wilt and release liquid.
Stirring occasionally, continue to saute the collard greens. Cover with a lid when you are not stirring.
When your collards are wilted, tender, and dark green, around 10 additional minutes, remove from heat. Taste and adjust the salt level if needed.