In a food processor, put all ingredients together to prepare the basil cream (basil, garlic, pine nut, olive oil, parmesan cheese) and blend them until they are incorporated.

In a pan, heat the olive oil, add the thyme and place the fish fillet. Season with salt and pepper, and cook for 2 minutes on each side to brown them slightly, turning carefully not to break up the fish. Finish with lemon juice, adding some stock and spinach and cook for 2 minutes longer.

Remove the fish; add the butter and the lemon zest.