Step 1: Wash the spinach thoroughly under cold water and pat it very dry with a clean kitchen towel or use a salad spinner. Mince the garlic cloves. Zest half of the lemon, then cut it in half and juice it. Grate your Parmesan cheese.
Step 2: Heat the olive oil in a large skillet or non-stick pan over medium heat. Once the oil is shimmering, add the minced garlic. Sauté for 30-60 seconds, stirring constantly, until the garlic is fragrant and lightly golden. Be careful not to burn it, as burnt garlic can become bitter.
Step 3: Add the fresh spinach to the skillet. If your pan is not large enough to hold all the spinach at once, add it in batches, allowing the first batch to wilt slightly before adding more. Using tongs, continuously toss the spinach until it has completely wilted down, which typically takes about 3-5 minutes. It will dramatically reduce in volume.
Step 4: Remove the skillet from the heat. Immediately stir in the fresh lemon juice, lemon zest, and grated Parmesan cheese. If using, add a pinch of red pepper flakes now.
Step 5: Season the sautéed spinach with salt and freshly ground black pepper to taste. Serve immediately as a delicious and healthy side dish. Enjoy!