Heat your oven to 200°C/Fan 180°C/Gas 6. Scrub your potatoes and chop into bite-sized chunks. Chuck into a pan and cover with boiling water. Bring back to the boil and cook for 5 mins. Drain and allow to steam dry. Tip back into the pan.
Cut off the outer leaves from your cauliflower, keeping the small tender ones for later. Break the cauli into bite-sized florets. Roughly chop the tomatoes. Add them both to the pan with the potatoes. Place a baking tray in the oven to heat up.
Halve the chilli, flicking out most of the seeds (leaving a few in for a kick). Finely chop. Peel and crush the garlic and scrape it into a pestle and mortar. Add 1 tsp turmeric, 2 tsp cumin seeds, half the chopped chilli and 2 tbsp oil. Pound it all together.
Pour this mix into the potatoes, cauli and tomatoes. Toss together with a pinch of salt. Tumble onto the hot baking tray. Roast for 30-40 mins, till the potatoes are soft and crisp at the edges. Toss halfway through the cooking time.
Meanwhile, make your kebabs. Spoon the yogurt into a large bowl. Add 2 tsp garam masala, a pinch of turmeric and the remaining chopped chilli. Zest in the lemon and add a squeeze of lemon juice. Pour in ½ tbsp oil. Heat your grill to its highest setting.
Cut any large pieces of fish in half. Add the fish to the yogurt mix and stir to thoroughly coat. Thread the fish pieces on 6-8 skewers. Keep a little space between each piece so they cook evenly and quickly.
Lay the fish kebabs on a foil lined baking tray and spoon over any remaining yogurt. When your roasted potato and cauliflower curry is 5 mins away from being cooked, slide the kebabs under the grill. Cook for 3-4 mins till cooked through, turning once. Take care not to over cook – they cook very quickly.
Tip the potatoes, cauliflower and tomatoes into a bowl. Stir through the spinach and saved cauli leaves to slightly wilt them. Serve with the fish kebabs and wedges of remaining lemon.