This is an easy, low-carb make-ahead supper. Well, it is easy if you buy a jar of olive spread (I used Ta’amti tapenade).
It also helps if you know how to cook “en papillote,” which is a French term for cooking something wrapped in paper. According to the dictionary, the term doesn’t come from “papier” (paper) but “papillon” (butterfly). Maybe because the paper is traditionally cut into a heart shape, folded in half, so it looks a bit like a butterfly? I don’t know . . . But, you can even more easily wrap the fish in a rectangular piece of foil and that will still accomplish the primary “en papillote” goal of trapping and infusing flavor during baking. I have made this fish in foil and in paper and both ways work.
Here is what you do: saute baby spinach with garlic and orange zest and then lay it on a piece of parchment or foil (traditionally, the paper is greased, but I didn’t bother and it was fine). Spread a piece of salmon with tapenade and place the salmon over the spinach. Squeeze over a little lemon juice. Wrap the fish up in the foil or parchment (here is how you crimp the parchment, if that is what you are using). Set the package aside in the refrigerator until about 20 minutes before you want to serve the fish. Then cook the fish and serve.
You could also make this fish without the paper or foil, just roasting it uncovered on a baking sheet. The spinach can be cooked separately on the stove instead of with the fish in the oven. The en papillote method seems to infuse the flavors more, plus you get a delicious blast of savory aromas when you open the package. Olive, orange and garlic fuse together, creating an aroma that is intense, almost meaty in its umami-ness (if that is a word).
The spinach all by itself is lovely, fragrant with garlic and a hit of orange that is both unexpected and yet absolutely right. If you want to make the spinach separately, you can just leave the spinach in the pan in which you wilt it, cover it and cook it another 20 minutes on low before serving.