The smoky flavor of this salsa pairs well with beef, and my mom always serves it alongside her brisket. In fact, I can always count on finding this salsa in her refrigerator. She and I like very spicy salsas, and we love the intensity of this one.
Add the canola oil to a medium skillet over medium heat. Add the chiles and toast for 1 to 2 minutes, stirring constantly so the chiles are fried well and change color. Add the onion and garlic and fry for 2 minutes, again stirring constantly.
Transfer the fried ingredients to a food processor or blender and add the whole tomatoes, tomato sauce, and salt. Purée until salsa is smooth with specks of chiles. Add salt to taste. Serve at room temperature or slightly chilled. Serve as a salsa dip or to top off your favorite tacos or tostadas.
Chile de arbol salsa can be stored in the refrigerator 3 to 5 days, or frozen for many weeks.