Preheat the oven to 425 degrees F. Dice the onion, and saute in the butter until brown and soft. Season with salt and pepper to taste.
While that’s cooking, rinse the spinach and rough chop it. Prepare the sheet pan with parchment paper.
When the onions are done, put the spinach in and turn off the heat. Season with a little salt and pepper.
When your veggies are done, spread them evenly over the parchment paper lined pan.
Then mix up some eggs with some salt and pepper and pour over the veggies.
Put it in the oven for about 7 minutes, until egg is set.
When the omelette is done, grate some cheese over the top. I used cheddar, but any cheese would be delicious.
Starting a short end, fold the edge of the egg over itself. Once you’ve got it started, use the parchment paper to lift the omelette into the roll.
When you’ve got it all the way rolled, use the parchment paper to pick it up to put it on a nice plate. And then grate a little more cheese on top. And maybe a sprig of parsley or chive if you have it. Serve it in slices.