Heat oven to 220C. In a 20cm x 30cm baking tray,place 60ml water with the tomato,roast for about 30 minutes until the tops of the tomato pieces are dark and charred. Allow to cool,strain liquid into a bowl and set aside,also reserving the pulp.
In a pan over medium heat,toast the clove,cumin and cinnamon until fragrant (about 1 minute),remove and reserve. Remove stems and seeds from the dried chillies,and tear into small pieces. Using the same pan over a medium heat,toast chilli until just smoking (1-2 minutes),transfer into a heatproof bowl,add 1 cup hot tap water and cover with a plate to ensure the chilli pieces are submerged. Allow to sit for 30 minutes,then strain.
In a small blender,blitz the spices and chillies,add the roasted tomato pulp and then blitz again.
In a saucepan,heat the grapeseed oil over medium-low heat and sweat the onion and garlic until tender (about 10 minutes),season with the sea salt. Add the tomato/chilli mix and simmer until a thick sauce consistency is achieved (keep in mind you still need to add the mezcal). Add the mezcal,cook for a moment and adjust seasoning.
Preheat barbecue to a high heat,drizzle prawns with a little oil and season with sea salt. Grill flesh side down first until lightly charred and just cooked through,(1-1½ minutes per side).
Serve with mezcal and tomato sauce and garnish with jalapeno,red onion and coriander.
Serve as part of Neil Perry's Mexican banquet (recipes here).