Heat a pan over a medium heat with the olive oil. Sauté shallot for 4-6 minutes until tender and lightly browned. Add the garlic, tomato puree, harissa paste and sugar. Fry for two minutes.
Move everything out to the sides of the pan and add the spices to the centre. Toast for 30 seconds, then stir to combine.
Add the cherry tomatoes and cook until they burst and blister, then add the water and allow to simmer until thick and sticky.
Season to taste with salt and fresh black pepper.