Heat a frying pan over a medium heat with NO oil, add the chillies tomatoes and garlic and cook until the skins are properly blackened - this will take 10-15 minutes.
Fear not for the smoke will fill the room- this means your salsa will be lovely and smoky- blend very lightly with a stick blender, puree is not what we are looking for.
Add the juice of 2/3 limes, a handful of coriander and half a finely chopped white onion and a pinch of sugar to balance the spice.