In a bowl, whisk together mayonnaise, sugar, apple cider vinegar, salt, and black pepper. Add in shredded cabbage and toss to dress. Refrigerate for 30 minutes before serving.
In a pan over medium-low heat, add the tomato paste. Saute for a few minutes until it caramelizes slightly. Add water and stir to dissolve the tomato paste. Add in apple cider vinegar, brown sugar, salt, worcestershire, liquid smoke, smoked paprika, black pepper, and cayenne pepper. Mix to combine.
Bring to a gentle boil and reduce until the sauce has thickened. Reserve half of the sauce and set aside to use when assembling.
Add in 2 cans of Wild Planet's Albacore Wild Tuna. Gently crush it with a fork to smaller pieces, as desired. Toss it in the sauce and remove from heat.
To assemble, add the BBQ tuna onto the bottom bun, top with coleslaw, and add the reserved BBQ sauce as desired. Top with the top bun and enjoy immediately!