Step 1

Set an oven rack about 6 inches from the heat source and preheat the oven's broiler to high.

Step 2

Spray a 9x13-inch glass casserole dish with cooking spray. Arrange tomatoes in the prepared dish with cut sides down. Add onion and jalapeno.

Step 3

Broil until tomato skins are blackened and blistered, 10 to 15 minutes. Remove onion and jalapeno halfway through cooking time, once skins are slightly softened.

Step 4

Combine broiled vegetables in a blender; add cilantro, lime juice, and 1 teaspoon garlic salt. Pulse until smooth. Taste and season with remaining garlic salt as desired.