Rinse the kale thoroughly under cold water
Remove the tough stems and tear or chop the leaves
Heat oil or butter in a large skillet or pot over medium heat
Add garlic or onion if desired and cook briefly
Add the kale to the pan in batches if needed
Pour in a small amount of water, broth, or stock
Cover and cook until the kale wilts, stirring occasionally
Uncover and continue cooking until tender
Season with salt, pepper, and optional vinegar or lemon juice
Serve warm