Place peppers in large, dry skillet. Toast over medium, stirring often, until darkened and fragrant, about 1 minute. Transfer to a bowl. Cover with hot water; soak 30 minutes. Remove stems.
Place garlic in skillet. Cook over medium, stirring often, until soft and lightly browned, about 15 minutes. Let stand until cool enough to handle. Remove and discard peels.
Preheat broiler with oven rack 4 inches from heat. Place tomatoes in a single layer on a rimmed baking sheet. Broil tomatoes until softened and charred, about 10 minutes, turning after 5 minutes. Let stand 5 minutes.
Transfer tomatoes and any pan liquids to a food processor. Add peppers, garlic, salt, cumin, sugar, and vinegar. Process until smooth, 1 to 2 minutes. Serve immediately, or store in an airtight container in refrigerator up to 3 days.