Chicken tinga: add a large skillet or pan to medium-high heat.
Add one tablespoon of olive oil to the pan and when it starts to shimmer, add diced onions, garlic, chipotle, adobo sauce, fire-roasted tomatoes, chili powder, and chicken broth. Stir to combine everything.
Bring the mixture to a simmer, stirring occasionally. After it starts to simmer, turn the heat down to medium-low.
Cover the pan and allow it to cook for 10 minutes.
After 10 minutes add the tablespoon of apple cider vinegar and stir everything up. Add chicken, stir and cook for another 2 to 5 minutes, until the chicken is warmed through.
Make the sandwich: toast your cemita buns if you prefer.
Spread avocado onto the bottom bun. Sprinkle with salt
Add a heaping quarter cup of chicken tinga on top of the avocado.
Top chicken with shredded Oaxaca cheese.
Sprinkle on a healthy amount of papalo or cilantro leaves.
Add the top of the bun to the sandwich. Serve and enjoy.