1. Make the beef and pickle: Heat the oil in a large skillet over medium heat. Add ¾ cup of the diced onion and the garlic and sauté until softened, about 4 minutes. Add the ground beef, cinnamon, paprika, cumin, chile powder, oregano, salt, and pepper and cook until the beef is no longer pink, about 8 minutes.
2. Add the tomatoes, chiles, pickles, and pickle juice. Reduce the heat to medium low and cook, stirring occasionally, until the juices thicken and the flavors have melded, 15 to 20 minutes.
3. Assemble the tacos: Spoon the ground beef mixture into taco shells and sprinkle with shredded cheese, shredded lettuce, the remaining ¼ cup diced onion, and some more diced pickle. Top with the sour cream and serve 2 tacos per person.