A piece of cod is a glorious thing. My favourite is Cod Pie, which I'll put up the recipe for, but you want something simple, and the recommendations here are excellent. En papillote is foolproof, and baking only slightly trickier. The famous Black Dog on Martha's Vineyard does/did excellent cod baked in rolled oatmeal, which needs just a little flour for adhesion.
But you don't even need heat to cook it. Slice it thin, toss with red onion slices and juice from two limes. Leave for 20 minutes, then drain. You'll notice that the cod turns opaque and looks cooked, because it is. Serve on tortillas with fresh cilantro, and call it ceviche.