Drizzle with olive oil and roast all but two of the tomatoes and garlic cloves (in their skin), ½ the white onion (roughly chopped), and 3 of the jalapeños (remove the stems) at 400 degrees Fahrenheit for 25 minutes.
Place the oven on broil and roast for 5-7 more minutes, turning the peppers and onions occasionally. (NOTE: Your goal is to get a decent char on the peppers and onions.)
Let everything cool down, and then place the roasted and and remaining non-roasted ingredients into a blender.
Pulse/chop the blender contents into desired consistency.
Remove contents from the blender into a serving dish and serve.