Having a jar of this in your fridge is brilliant. My favourite way to eat it is with oily fish, such as mackerel or sardines. The rose petals are delicate and fragrant, and nicely balance the heat of the chillies.
You can pretty much eat any garden rose, just make sure they haven't been sprayed with pesticides. If you can find some really wonderful-smelling roses, you’ll notice their fragrance will come through in the harissa.
Although you could chop all of this by hand, it will take you a while, so I suggest using a food processor. However, if you are doing it by hand you might want to wear some rubber gloves to protect you from the chillies as their juices might irritate your skin.
Preheat your oven to 150°C/300°F/gas 2. Spread the tomatoes (cut-side up), chillies and garlic on a large roasting tray, drizzle with olive oil and season. Place in the oven and roast for 1 hour, giving the tray a little shake a few times while cooking.
After an hour, remove the tray from the oven and leave to the side to cool. Once the chillies are cool enough to handle, put on some rubber gloves, remove their stalks and deseed them. You can do this under running water, as it helps with washing the seeds away. Peel the garlic cloves and place in the food processor with the chillies. Pulse until roughly chopped, then add the cumin, coriander and paprika, season well with salt and pepper and pulse again.
Next, add the tomatoes, rose petals, rose water and sugar, and pulse until you get a chunky paste, with lovely flecks of tomato and rose petals.
Transfer the paste to a bowl and stir in a splash of red wine vinegar and the extra virgin olive oil. You should have a beautiful, deep, reddish paste. Have a taste - you want a good balance between the heat of the chillies, the smoky paprika, the sharpness of the vinegar and the fragrant rose petals. Season again and add another splash of vinegar, if needed. Once you’re happy with the taste, spoon into a sterilised jar and keep in the fridge for up to a month.