Here’s one not mentioned. Preheat the oven to 350F. Put some butter in a pan and, over medium heat, fry a nice chunk of salmon that you rubbed with some spices that you like. If you start with the non-skin side, brown it to barely golden, then gently flip it to skin-side down and let it brown that side a while. Then take the whole thing, still in the pan and finish it off in the oven. That’s a wonderful thing about cast iron - can go from cooktop to oven and back, no problems. I do this all the time, but more often with steaks. Check the internal temp of your salmon with a thermometer. Fish is done between 150F and 160F, depending on your preference.
If you have two cast iron pans and a surplus of butter and olive oil, you can make potatoes Anna about 30 minutes before you start the fish. Cast iron can stick potatoes to the bottom, so use very generous portions of the fats to cook those potatoes to a rich golden brown top and bottom.
Pommes Anna is simple to make. Slice up a bunch of clean potatoes, leaving the skins on. Make them 2-3mm thick. In a bowl toss them with salt, pepper, olive oil and melted butter. Put extra olive oil in the pan. Layer the potatoes in it, really packing them in. Then stick it in the oven. They are done when they look like this on the sides, as your finishing maneuver is to invert them on a plate. Since it’s cast iron, you might need to take them out of the oven, let them rest a minute or two in the pan, then release them from the bottom of the pan with a spatula before inversion.