Preheat oven to 200˚C/400˚F
Boil potatoes – place in a saucepan and cover with cold water. Bring to the boil and then boil for 10 mins, until just tender.
Drain, then put the lid back on the saucepan and give a little shake to rough up edges of the potatoes.
Tip out into roasting tin, add the unpeeled garlic cloves and fresh rosemary and drizzle with 2 tbsp olive oil, and season with salt and black pepper. Roast for 15 minutes, then stir the potatoes and check the garlic cloves – if they are soft take them out, as they will cook quicker than the potatoes. Return the potatoes to the oven for another 30-40 minutes, until they are golden all over.
Meanwhile, make the sauce: Fry the onion in olive oil over a low/medium heat until soft. Add the garlic and cook for 1 minute before adding the tomatoes, water, smoked paprika, ground cumin, cayenne/tobasco, and season. Simmer gently for 15-20 minutes until thick – when you drag a spoon across the pan the juices don’t instantly fill the gap it left.
To make the aioli: in a bowl mix the mayo and Greek yogurt together, squeeze the roasted garlic out of the skin and beat into the yogurt mixture with the lemon juice and black pepper. Put to one side until ready to serve.
As soon as potatoes are ready, spoon them into heatproof dish and pour over the tomato sauce. I like to leave the garlic aioli on the side for people to add/dip into as they wish, but you could drizzle it over the top if you prefer.