1. Heat the oil in a medium saucepan over medium-high heat until it shimmers. Add the tomatoes and jalapeños, standing back to avoid splatters. Cook, stirring frequently, until the tomatoes are very soft, 5 to 10 minutes. Taste and season with salt as desired. For a smoother salsa, puree in a food processor or blender. The salsa keeps for up to 1 week, covered and refrigerated.