In a very large, deep pot, heat the olive oil over medium heat for 3-4 minutes. Add the garlic and sauté for about 1 minute, until no longer raw but not browned.
Add the spinach, carefully mixing it with a wooden spoon to coat the leaves in the olive oil. Depending on how deep your skillet is, you might need to add it in several batches, as I do in the video below.
Cook the spinach, stirring with a wooden spoon, until it's just wilted, about 3 minutes.
Turn the heat off and stir in the salt, pepper, lemon juice, and butter. You can also reserve the butter for topping the spinach after you remove it from the pan, as I do in the video. It makes for a pretty presentation.
Using a slotted spoon, transfer the spinach to a serving bowl. Serve immediately.
Video
Notes
While one pound of spinach may seem like a lot, remember that spinach loses a lot of volume as it cooks. So this is a good amount of spinach for four people.
That's why you need a large, deep skillet or saucepan when making this recipe - to accommodate the large volume of raw leaves.
You can cook the spinach in ghee instead of olive oil. It adds a wonderfully nutty flavor.
You can keep the leftovers in the fridge, in an airtight container, for up to three days. Reheat them in the microwave, covered, at 50% power.