lettuceleaves and Tarragon & mustard mayonnaise (see 'goes well with', below), to serve
To make the relish, fire up the barbecue and, while it’s blazing, char the pepper and chilli. Put in a bowl and cover with cling film. Meanwhile, char the red onion and tomato. When cool enough to handle, peel the tomato, then peel and deseed the pepper and chilli (leave in the chilli seeds if you want to add some heat). Tip the charred veg into a food processor with the lime, oil and cumin seeds, then season and pulse a couple of times to keep it chunky, or leave the machine running to make a smooth relish.
For the steaks, mash the garlic with the lime juice, olive oil and thyme, then spread over the meat. When the coals are ashen, cook the steaks for 4 mins on each side for medium-rare, adding or subtracting 1 min either way to cook to your liking. Leave to rest for 5 mins, then carve into thick slices. Put the steaks on a board with the baguette, lettuce, relish and Tarragon & mustard mayonnaise, and let everyone assemble their own sandwich.