1. For the vinaigrette, put the oil, shallot, garlic and thyme in a small, cold saucepan with a good pinch of salt. Place over a low heat and warm up gently. The aim is to poach the shallot for about 20 minutes, with just a few bubbles coming up now and then. The shallot and garlic should soften but take on no colour. Take the pan off the heat, stir in the vinegar and leave to cool completely.
2. Heat the barbecue or griddle pan over a medium heat. Cut 3 slits down each side of each fish, through the skin and flesh but not quite done to the bone, and stuff the cavities with the lemon slices and thyme.
3. Cook on each side for 3-4 minutes, then check the flesh is cooked – it should be opaque and come away from the bone. (If you’re unsure, you can always pop them in the oven at 180C/fan oven 160C/gas mark 4, for 5 minutes.)
4. To finish the vinaigrette, discard the thyme and garlic and stir in the tomato and herbs. Spoon the vinaigrette over the cooked fish to serve.

This is the perfect dish to make when you want to get the barbecue going but you fancy something lighter. Sea Bass takes on the smoky charcoal flavour so well and the shallot vinaigrette goes perfectly with the white fish, but also works well with Tuna and Salmon.