Shred the chicken using two forks into thin strips. To a skillet, add the shredded chicken, chili powder, smoked paprika, garlic powder, onion powder, black pepper, and salt. Sauté for about 3 minutes until fragrant.
Turn the heat to low and add the barbecue sauce to the chicken. Mix to combine until all the chicken is well coated. Cook for about 2 minutes, then turn off the heat and transfer the chicken to a bowl.
Cut the tomatoes into medium-thick slices and slice the hamburger buns in half. Preheat a large nonstick skillet over medium heat, then add 1 tbsp of butter. Add the buns cut side down on the skillet and toast until golden brown.
Begin assembling the burgers. Add 1 tbsp mayonnaise to the bottom half of the sliced buns, followed by lettuce, a slice of tomato, and ¾ cup of barbecue chicken. Then, place the top slice of the bun on top.
Top with more barbecue sauce if desired. Serve with a side of fresh salad or roasted veggies. Store any leftovers in an airtight container in the refrigerator for 3-4 days.