How to Make It
Fill a small pot with water and bring to a boil. Blanch the tomato until its skin has shriveled and it is heated through, about 2 minutes. Drain and reserve on a paper towel until cool enough to handle. Remove the skin and core.
Roast the habanero under a broiler or in a dry skillet until soft and charred all over, about 3 minutes. Remove the habanero stem and discard.
In a blender or food processor, blend the tomato and habanero until smooth. Salt to taste.
Heat the oil in a large saucepan over medium heat, then add the onion and sauté until it’s soft, about 5 minutes.
Add the tomato-habanero mixture and cook for a few minutes, until slightly thickened and fragrant. Thin with water or chicken stock if needed to make a cohesive salsa.