Chop the Roma tomatoes.
Destem and deseed the peppers.*Wear gloves during this process. Add 2 cups of water to a skillet and bring to a boil.
Add the peppers to a frying pan over medium heat and toast for 1-2 minutes on each side.
Turn the heat off and place the toasted peppers in the pan with the boiling water. Cover the pan with a lid and let the peppers soak for 20 minutes until they are very soft.
While the peppers are soaking, add the olive oil to the frying pan (the one you used to toast the peppers) over medium-high heat.
Add the onions to the pan and saute for 10 minutes stirring frequently. until they begin to lightly caramelize
Add the garlic to the pan and cook for 1-2 minutes until it becomes fragrant
Add the Roma tomatoes, tomato paste, cinnamon, cumin, dried oregano, and brown sugar to the pan.
Stir to combine and cook for 2-3 minutes over medium heat.
Add the salt and pepper to the pan. Stir to combine.
After 20 minutes, drain the peppers and reserve the liquid.
Add the apple cider vinegar and ½ cup of the reserved pepper liquid into the skillet. Stir to combine and simmer for 5-7 minutes until the liquid has reduced.
Place the soaked peppers and the tomato-onion mixture into the bowl of a food processor.*Make sure to scrape all the brown crunchy pieces out of the bottom of the skillet before adding them to the food processor. Pulse the ingredients until smooth and creamy.*If the adobo is too thick, add more of the reserved pepper water, 1 tablespoon at a time to get your desired consistency.