For the tortillas, boil the lentils until soft 20-25 minutes, drain and transfer to blender, mix until smooth. Mix tortilla flour with half the water, the lentils, salt and add remaining water until smooth dough is achieved. Allow to rest for 10-15 minutes.
Heat up skillet. Divide dough in roughly 50g balls, roll each portion into a circle and transfer individually to the hot skillet. Allow to cook until lightly brown and easy to remove (1-2 min), flip and cook other side. Keep tortillas warm in a tea towel, allow tortillas to sit for 10 minutes before eating.
For the fish, mix the all-purpose flour with the spices. Cut the fish without skin or bones into strips, and coat with the flour and spice mix. Heat up olive oil in a frying pan and add the coated fish strip, fry for 2 minutes each side until golden. Transfer to paper towel to remove excess oil.
For the guacamole, dice avocado and mix with chopped tomato and coriander. Mix using a fork and add some lime pressed extra virgin olive oil. Season to taste with salt and pepper.
Build the taco - add guacamole to tortilla, the cucumber, and the fish strips. Top with red onion, chipotle mayo and coriander.