Step 1

Purée tomatoes, onion, chiles, garlic, and bouillon powder, if using, in a blender until smooth.

Step 2

Heat oil in a large skillet over medium. Carefully pour tomato mixture into pan; it will spit and bubble, so stand back! Cook salsa, stirring occasionally, until thick and darker in color, 20–30 minutes. Let cool.Do ahead: Salsa can be made 2 days ahead. Transfer to an airtight container and chill.\