Preheat an offset smoker for cooking at 250 degrees F.
Rub pork collar generously with dry rub. Place pork in smoker and cook, brushing with Honey BBQ Glaze every hour, until internal temperature reaches 150 degrees F, about 5 hours.
Let rest for 15 to 20 minutes, then slice into 1/4-inch slices.
Meanwhile, put tomatoes in a pan, drizzle with 4 to 6 tablespoons olive oil, and sprinkle each side with dry rub. Cover with foil and smoke in smoker for 1 hour.
Meanwhile, place onions in a medium saute pan with 2 tablespoons olive oil. Cook over low heat until onions are caramelized, soft and golden brown, 1 to 2 hours. Mash onions into a chunky paste.
Slice open bolillo bread. Melt butter in a large saute pan or comal over medium-high heat. Place bolillo bread pieces in the pan cut-side down and cook until golden and toasted. Drizzle 2 tablespoons olive oil into the same pan. Place sliced pork collar into pan. Drizzle each side with Honey BBQ Glaze. Sear each side of pork for 2 to 3 minutes. (You may also use this same pan to warm up cooled smoked tomatoes, if needed.) Build 6 open-faced sandwiches, spreading a generous layer of caramelized onion paste on each piece of bread, layering the pork on top, layering on smoked tomatoes and drizzling with Honey BBQ Glaze.
For the BBQ sauce: Preheat an offset smoker for cooking at 225 degrees F.
Whisk together the ketchup, vinegar, mustard, onion, Worcestershire, pepper, dry rub and granulated garlic in a stainless steel or cast-iron pot until smooth. Place in smoker to cook until darkened, medium-thick and the onions have softened, 4 to 6 hours. (Alternately, cook BBQ sauce in a pan on the stovetop over low heat, covered, 4 to 6 hours.)
For the glaze: Whisk together honey with 2 1/2 cups BBQ sauce until smooth and creamy (save the remaining BBQ sauce for another use).
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of Valentina's Tex Mex BBQ, Austin, TX