How to Make It
In a medium saucepan, combine the sun-dried tomatoes with the vinegar and 1 1/2 cups of water and bring to a boil. Remove from the heat, cover and let stand until the tomatoes are very soft, about 1 hour. Drain, reserving 1/2 cup of the soaking liquid.
Meanwhile, preheat the broiler. Brush the chiles with olive oil and broil 6 inches from the heat, turning occasionally, until they are lightly charred all over, about 10 minutes. Transfer the chiles to a bowl, cover with plastic wrap and let stand until cool. Peel and seed the chiles.
In a medium, deep skillet, heat 1/2 cup of the olive oil. Add the garlic and cook over moderate heat until softened, about 2 minutes. Add the onion and cook until softened, about 5 minutes. Add the plum tomatoes and the sugar and cook until the liquid is evaporated and the tomatoes begin to break down, about 5 minutes.
Scrape the tomato-onion mixture into a food processor. Add the chiles, sun-dried tomatoes and their reserved 1/2 cup of soaking liquid and process until smooth. Strain the puree through a fine sieve to remove the seeds and skins. Stir the remaining 1/4 cup of olive oil into the puree and season the salsa with salt.