I realize that there is already one egg sandwich with tomato jam in the archives of this site, but I can’t resist sharing my current favorite incarnation.
It starts with a pat of butter melted in a very well seasoned cast iron skillet. I bought this square one on eBay many years ago and it’s one of my very favorite pieces of cookware. Once the butter is just melted, I pour in two beaten eggs and tilt the pan to get an even coating.
While the eggs cook, I line the top of the eggs with spinach leaves. You want to get them in there while the eggs are still quite loose, as then they cook into the eggs and will stay in place when you flip.
Then you ease a spatula under the eggs (taking care to work all around so that you know nothing is sticking) and flip. This takes some practice, but as long as the skillet is well seasoned and you used butter (coconut oil also works), you should be able to do it.
Once the eggs are flipped, I turn off the burner and let the residual heat in the pan do the rest of the cooking. This is also the point at which you add some cheese. Cheddar is nice, but dill havarti or creamy goat cheese are also favorites.
I make one fold and add a goodly dollop of tomato jam. Another good option is a caramelized onion jam (there’s a recipe I like a lot in Preserving by the Pint). Fold again and place between two slices of toasted bread. You can also roll it up into a tortilla if you’re feeling more like a wrap than a sandwich.
Then, you wait until the sandwich cools ever so slightly (molten hot cheese burns are no good) and then you dig in. The sandwich makes enough that you could cut it in half and share it with a friend if you’re feeling generous.