Heat a very large skillet (that has a cover available) over medium heat. Add oil. If using garlic, add garlic to hot oil and sauté for 1 minute, stirring constantly. Don't let it scorch.
1 tablespoon extra virgin olive oil, 1 clove garlic, minced
Add spinach, salt, and pepper and toss to coat with oil. If all of the spinach doesn't fit into the pan, add what you can and let it cook for a couple of minutes, then add the rest. Cover and cook for 3 minutes or until spinach has wilted slightly. Note: If the spinach leaves are completely dry, add a splash of water to the pan so the spinach will steam.
16 ounces baby spinach, ½ teaspoon kosher salt, ¼ teaspoon coarse ground black pepper
Uncover and stir, cooking for another 3 to 4 minutes or until spinach is completely wilted and cooked to your liking, and most of the liquid has evaporated.
Stir in lemon juice, if desired, and serve immediately.
1 teaspoon fresh lemon juice
Video
Notes
Yield: Spinach is mostly water so it really cooks down. Even though 16 ounces of spinach may look like a LOT of spinach, you'll end up with roughly one cup of cooked spinach, depending on long you cook it. The more you cook it, the more it will shrink down.
Pro tip: Don't overcook baby spinach. It tends to get slimy or mushy, and may taste bitter. It's best when it's lightly sautéed.
Choosing spinach: If you prefer, substitute regular spinach for baby spinach. Baby spinach is harvested when the leaves are very small (15 to 20 days) and regular spinach is allowed to mature (45 days). Add a little more cooking time if you're not using baby spinach.