Oven temperatures vary, adjust the cooking time accordingly. The doneness of the fish also relies on its thickness. Leave it whole instead of portioning into pieces, I like the rustic look as you serve, the idea of sharing one whole piece with your family and it always comes out perfectly moist). To test the doneness, push the fish with your fork, if it's opaque and flake easily, that's done. Cooking salmon should not be that complicated even without too many gadgets