Roast the fresh tomatoes on a rimmed baking sheet 4 inches below a preheated broiler until blackened and blistered, about 6 minutes per side. Cool, then peel (if you wish). Scoop the tomatoes (fresh roasted or canned roasted) into a blender or food processor, along with all their juices. Puree and set aside.
Roast the poblanos over a gas flame or 4 inches below a preheated broiler, turning frequently, until blackened all over, about 5 minutes for the open flame, 10 minutes under the broiler. Collect in a bowl and cover with a kitchen towel. When cool rub off the blackened skin and pull out the stem and seed pod, then tear the chiles open, scrape out the seeds and rinse briefly under cold water to remove stray bits of skin and seeds. Chop into ½-inch pieces.