Grill the red peppers: Heat the grill to a high temperature. Pierce the red peppers and grill for 15 minutes until tender and blackened. Alternatively roast them over the gas burner.
Tip: Place them in an air tight container or a heat-proof plastic bag and close tightly while they are still hot. The steam will make peeling the peppers easier. Open the container or the plastic bag in a few minutes and remove the charred skin.
Toast the spices (Skip if using ground spices): Place the coriander seeds, the cumin seeds and the cardamom seeds (removed from the pods) in a dry, cold pan and gradually heat them over medium fire. Toast for a couple of minutes. Allow to cool and grind them using either a coffee grinder or a mortar and pestle.
Sauté the onion and garlic: Heat one tablespoon of olive oil in a pan. Chop the onion and mince the garlic. Sauté the onion and garlic with the olive oil for 5 minutes until golden brown. Add a pinch of sugar and cook for two more minutes before removing from the heat.
Make the spicy Harissa Dip: Place all the ingredients in a blender or a food processor and process to create a smooth paste. If the paste gets too thick, drizzle a little more olive oil or tomato paste and blend again.