How to Make It
In a large saucepan, heat the oil. Add the fennel, garlic and a pinch of salt and cook over moderate heat, stirring occasionally, until softened, 15 minutes. Add the tomatoes and vinegar and bring to a boil. Simmer over moderate heat, stirring frequently, until nearly all the liquid has evaporated, about 10 minutes. Transfer to a blender. Add the gochujang and puree until very smooth. Season with salt and let cool completely, then refrigerate until chilled.