How to Make It
Preheat oven to high broil with rack positioned 5 inches from heat source. Arrange tomatoes, cut sides up, on a rimmed baking sheet. Sprinkle evenly with 1 tablespoon of the salt. Broil in preheated oven until tomatoes are slightly charred and skins blister, about 15 minutes. Carefully remove from oven; let stand until cool enough to handle, about 15 minutes. (Do not turn oven off.)
Using your hands, peel tomatoes over baking sheet, reserving any tomato liquid; discard tomato skins. Transfer peeled tomatoes and liquid to a large bowl. Crush tomatoes into small chunks using your hands or a whisk. Set aside.
Toss together poblanos and 1 tablespoon of the oil on a separate baking sheet. Broil until blistered, about 12 minutes, turning once halfway through cook time. Transfer to a heatproof bowl; cover tightly with plastic wrap. Let stand 10 minutes. Remove and discard skins and seeds from poblanos. Chop poblanos.
Heat remaining 3 tablespoons oil in a large Dutch oven over medium-high. Add onions and garlic; cook, stirring occasionally, until onions just turn translucent, 5 to 6 minutes. Add tomatoes (and any accumulated liquid), poblanos, vinegar, sugar, cumin, and cayenne. Bring to a boil over high. Reduce heat to medium; simmer, stirring often, until mixture has thickened and little to no liquid pools on the surface, 10 to 12 minutes. Remove from heat; stir in cilantro, jalapeños, and remaining 1 tablespoon salt. Let cool to room temperature, stirring often, about 1 hour.
Spoon salsa evenly into 5 (1-pint) lidded jars. Cover and store in refrigerator up to 10 days. Alternatively, process in a water bath in canning jars for long-term storage.