Gather your ingredients and heat a large sauté pan over medium heat. Add the olive oil and wait until it shimmers and releases a fruity aroma.
Add the minced garlic to the hot oil and cook, stirring constantly, until fragrant and just beginning to turn golden, about 30 seconds.
Gradually add the washed spinach to the pan in batches, tossing with tongs or a spoon to coat with garlic oil. Continue adding until all spinach is in the pan.
Toss the spinach continuously as it wilts down, about 2-3 minutes, until all leaves are tender but still vibrant green and glossy.
Season with salt to taste, then squeeze in the lemon juice and sprinkle with red pepper flakes if using. Toss again to combine all flavors evenly.
Remove the pan from heat. Finish by cracking freshly ground black pepper over the spinach and giving it a final toss.
Transfer the sautéed spinach to a serving dish immediately while still warm. Drizzle with a little extra olive oil if desired, and enjoy its tender, glossy appearance and fragrant aroma.