Dice the onion and carrot, then add to a large pan with half of the olive oil. Cook over a medium heat for 3 minutes, then add the lentils (including the liquid), chopped rosemary and vinegar. Put a lid on and simmer for 20 minutes.

Add the spinach to the lentils and allow to wilt. Turn the heat down to low and season.

Season the sea bass with salt and pepper. Pour the remaining oil into a frying pan and put on a medium-high heat. When the oil is sizzling, add the sea bass skin side down and cook for 4 minutes (depending on size). Flip over and cook for another 30 seconds.

To serve, ladle a portion of lentils into each bowl, then add the fish. Top with a small dollop of natural yoghurt.