Step 1

Arrange a rack about 4 inches below the broiling unit, and set the oven to broil. Place the tomatillos, pepper, and garlic on a rimmed baking sheet, drizzle with the oil, and toss to combine. Spread into a single layer. Broil until the tomatillos start to soften and are blackened in spots, flipping halfway through, about 8 minutes total. Cool completely.

Step 2

Transfer the tomatillos, pepper, garlic, and salt to the bowl of a food processor fitted with the blade attachment or a blender and add the salt. Blend until the tomatillos are puréed and the sauce is well-combined, about 30 seconds.