Cut the cauliflower into big florets and add into a food processor. Add the walnuts and pulse a couple of times. Keep pulsing a few times until everything is completely combined and grounded.
Transfer the mixture to a baking tray. Add half of the spice mixture (cumin, coriander, cloves, cinnamon, black pepper, nutmeg, and salt) and drizzle some olive oil on the top.
Bake for about 20 minutes at 180C (350F) stirring the mixture halfway through. When the mixture is cooked turn off the oven and leave aside.
Finely chop the onion, carrot, mushrooms, and mince the garlic.
Heat some oil in a big saucepan and add the onions. Stir for a couple of minutes until softened. Then add the garlic, carrot, and mushrooms.
Leave cooking for 10-12 minutes. Add the chopped tomatoes and the other half of the spice mixture, oregano, and bay leaf. Stir until all the ingredients are perfectly combined.
Lower the heat and leave simmering for at least 20 minutes. Adjust with sugar if the sauce is too acidic.