First, bring the ingredients for the marinade except the tofu to a boil in a pot and simmer for 10 minutes. Cut the tofu into 5 mm thick slices and place in a small baking dish. Pour the marinade over it. Leave to marinate for about 5 hours.
In the meantime, wash the lettuce and tomatoes, peel and slice the onion. Halve, pit and peel the avocado. In a bowl, mash the avocado with a fork and mix with the squeeze of lime juice.
