Add the oil and onions to a large pot and cook 3-4 minutes. Add garlic and cook for another minute.
Pour the onions and garlic along with the tomatoes through the peppers into a blender and liquify. Pour it back into the pot.
Add the chicken and bring to a simmer.
Add salt or adobo to taste.
Spread each taco shell with sour cream and beans, then top with chicken. Add whatever toppings you like.