Heat the butter in a large, deep skillet over medium-high heat. Add the garlic and cook it for 30 seconds. You want it golden but not burnt, so keep an eye on it.
Add the kale in batches. Stir-fry until the kale is tender and slightly wilted, for about 5 minutes.
Stir in the salt, black pepper, and lemon juice.
Serve immediately.
Video
Notes
Make sure to avoid overcooking the kale. You want it to have some "bite," just like al-dente pasta. You don't want it mushy and limp.
The reason for adding the kale in batches is that, much like spinach, it has a lot of volume when raw, but when it's cooked and wilted, it loses a lot of its volume.
Two great additions: when the dish is done, turn off the heat and sprinkle it with grated parmesan or bacon bits.
You can keep the leftovers in an airtight container in the fridge for 3-4 days. Reheat them covered in the microwave.