Hot-smoked mackerel tostadas with salsa and chipotle mayo

8 corn tortillas

300g hot-smoked mackerel fillet

For the tomato salsa:

4 very ripe tomatoes, chopped

1 tbsp red or white onion, chopped

1 clove garlic, crushed

½-1 chilli, deseeded and finely chopped Jalapeno or Serrano

1-2 tbsp chopped fresh coriander

squeeze of fresh lime juice

salt, freshly ground pepper and sugar

For the chipotle mayonnaise:

225ml mayonnaise

1½ tbsp puréed chipotle chillies in adobo

juice of 1 lime

1 tbsp chopped coriander

pinch of salt

To serve:

1 head lettuce, shredded

deep-fried shallots

avocado

lime juice