Heat your oven to 200°C/Fan 180°C/Gas 6. Scrub the potatoes and chop into 2cm-thick dice. Scatter into a large roasting tin. Sprinkle over 1 tsp Cajun spice mix and a generous pinch of salt and pepper. Pour in 1 tbsp oil and toss everything together to coat evenly. Roast for 30 mins, turning halfway.
While the potatoes roast, make the pumpkin seed salsa. Tip the pumpkin seeds into a small food processor and add the coriander, leaves and stalks, and the mint leaves. Halve the chilli, scoop out the seeds and pith, roughly chop the chilli and add it to the processor (this week’s chillies are hot, so make sure you scoop out the seeds and pith and only use half for a milder salsa).
Roughly chop the tomatoes and add them to the processor. Grate in the lemon zest and pour in 1 tbsp oil. Add a little salt and pepper and blend till everything is finely chopped. No food processor? No problem. Simply chop everything as finely as possible and stir together in a bowl. It’ll be chunkier, but still just as good. Set aside.
Slice the mini romaine lettuces vertically into quarters. Set them aside.
Sprinkle a little salt and pepper onto the cod fillets. Pour 1 tbsp oil into a frying pan and bring to a medium-high heat. Add the cod and fry for 3 mins on each side, till the flesh is pearly white and flakes away easily. Transfer to a baking dish and slide onto the bottom shelf of the oven to keep warm.
Add the lettuce quarters to the pan and fry for 2 mins on each side, till slightly wilted and golden.
Pop the cod on warm plates alongside the cooked lettuce and crispy potatoes. Spoon over the salsa and serve with wedges of lemon for squeezing.