Preheat oven to 200°C. Cut the ends off each aubergine, then cut in half lengthways. Pierce the flesh a few times with a knife then rub with olive oil and sprinkle with salt. Bake for 40 - 45 minutes or until flesh is browned, collapsed, and very soft.
Heat oil in a saucepan over medium heat and fry onions, garlic along with a good pinch of salt until soft. Add cumin, coriander and chilli flakes, and cook gently for 1 minute. Make sure onions and spices don’t dry out. Add a splash of oil if needed.
Next, add tinned tomatoes, stock, vinegar and sugar, bring to a boil, then cover and turn to simmer for 20 minutes.
When aubergines are ready, remove from the oven and let them cool for 5 minutes. Using a spoon, scrape out the flesh from the aubergine casing. Chop with a large knife until almost like a mash / puree.
To finish the sauce: add the mashed aubergine to the tomato sauce along with the sumac. Bring to a boil again then cover and turn to simmer for 10 more minutes.
Remove pan from heat, add a squeeze of lemon juice, a very generous pouring of olive oil and finally stir through flaked almonds. Taste and season with salt and pepper as needed. The sauce should be thick and glossy.