Place spinach in a colander and wash under cold running water. Let it sit for 10 minutes to drain excess water.
In a big skillet, heat oil over medium heat.
Saute onion for a minute then add garlic and cook until golden brown.
Add spinach and cover with lid for a minute. Spinach at the bottom will start to wilt and release some liquid.
Stir a few times and cover again until all spinach are wilted.
Add fresh ground black pepper and garlic powder. Salt to taste, if desired.
Transfer right away to a serving platter.
Serve with your favorite meat or seafood.
You can use pre-packaged baby spinach or spinach sold in bundles. Pre-packaged spinach are pre-washed but I suggest to wash it before cooking. They are sold in big bags or plastic containers. Add cold running water to container until spinach is covered. Soak for 5-10 minutes. Secure lid and leave a small opening on one side at the bottom and drain water. Leave it tilted in the sink for another 5 minutes to drain excess water or use a colander, whichever is easier for you. You can also use a salad spinner to drain excess water (I skip this step and I prefer it not too dry. Some liquid is needed to cook.)
If using spinach in bundles, cut the hard stem and discard. These are not pre-washed. Soak in water twice to remove dirt and place in a colander or salad spinner to drain excess water. Cut leaves into 3 portions.
Use your biggest skillet or a large pot.
Refrigerate leftover in an airtight container up to 2 days. Reheat in the microwave for minute or so.