Cut the lemon in half, cut one half into wedges for serving later, then squeeze the juice of the other half on to a large plate and add 1 tablespoon of tikka paste.
Mix together, then massage all over the frozen fish and leave aside in a single layer to marinate and defrost.
Peel and slice the onion, garlic and ginger with the chilli and coriander stalks, then place it all in a large casserole pan on a medium heat with a lug of oil and the remaining tikka paste.
Peel the potatoes, cut them into 2cm chunks, then stir them into the pan and cook everything for 15 minutes, or until softened, stirring occasionally. This will build up great flavour.
Quarter the tomatoes, add to the pan with the cauliflower, lentils and 600ml of boiling water, and bring back to the boil. Simmer for 45 minutes, or until the lentils are cooked through and the sauce is lovely and thick, adding splashes of water, if needed, then season to perfection.
Around 15 minutes before the curry is ready, put 1 mug (320g) of rice and 2 mugs of boiling water into a pan with a pinch of sea salt and the cloves. Cook on a medium heat, with the lid on, for 12 minutes, or until all the liquid has been absorbed.
Dry-fry the fish in a large non-stick pan for 3 to 5 minutes per side (depending on the thickness), or until charred, gnarly and cooked through – don’t be tempted to move it around, just let it colour and crisp up nicely.
Stir half the yoghurt through the curry and dollop the remaining yoghurt on top. Fluff up the rice, flake the fish on top, then sprinkle with coriander leaves and serve alongside the curry, with lemon wedges for squeezing over.