The lentils start cooking before the halibut, and if Roasting Radishes they can share the oven with the halibut, but also start them before searing the fish.
Exact cooking time for the halibut will depend on how thick it is, how well done you like it and how hot and long you sear for.
A fork easily breaks apart the fish when done.
And there are no Carbs until the Lentils arrive.
Remove from skillet and serve on top of lentils or rice if you prefer, with a squeeze of half a lemon.