Slice the tomatoes and jalapenos in half lengthwise and set them onto a cast iron pan or baking sheet, skin sides up
Add the onion and garlic cloves
Set the pan into the center of the oven and broil for 20 minutes, or until the skins of the tomatoes and peppers blister up. Do not allow to burn
Remove from heat and cool slightly
Remove the skins from the tomatoes, peppers and garlic. Discard them
Add the tomatoes, peppers, garlic and onion in a food processor along with cilantro, lime juice, Worcestershire, cumin, black pepper and salt
Process until smooth