Brush the bell peppers and garlic with oil and sprinkle with salt. Place the garlic on an oven tin layered with baking paper. Place the Peppers on top of the garlic, like a dome. This will catch steam and help the garlic cook much faster without burning (at the same time as the pepper will).
Roast for about 20 minutes until the peppers are dark brown, transfer them into a bowl, cover with cling film, and set aside.
Toast all the seeds in a dry pan for about 1 minute, then crush using a mortar and pestle.
Press out the flesh of the garlic and add it into a food processor. Add the pepperoni, about 1 tsp of the spice mix, and lemon zest, and blend. Once the bell peppers have cooled down slightly, peel off the skin, add them to the food processor, and blend well. Depending on your food processor, you may add the oil now and blend until smooth and creamy, or realize this whole thing would be much easier using a stick blender. In this case, transfer into a tall container and stream in the oil while blending.
Cut the cucumbers lengthwise in half. Cut into 4 cm segments, then slice each piece very finely, leaving one end barely attached. Press down the segments lightly so they would fan out. Season them with salt and lemon juice. If you're not in a hurry or very hangry, allow your cucumber to marinate for 10+ minutes before adding about 3 tbsp of your "harissa" mix well, and sprinkle with some coriander leaves.