In a large saute pan over medium-high heat, add the grapeseed oil. Season the fish with salt and pepper and add to the pan. Sear the fish for 3 to 4 minutes on each side. Add the thyme and juice of 1/2 a lemon and baste the fish with the sauce. Remove the halibut from the pan to a serving platter. Add the olive oil to the pan and stir in the tomatoes, the garlic and the juice of 1/2 a lemon. Cook for 2 minutes and then add the parsley. Stir to combine and serve on top of the fish.