To make the filling, in a large skillet, heat the oil on medium-low heat and add the onion and jalapeño. While stirring occasionally, cook until the onions and jalapeño are softened, about 5 minutes. Add the garlic and cook for 30 more seconds.
Add to the skillet the ground beef, chili powder, cumin, oregano, salt, pepper, tomatoes, and cilantro. Stir until everything is well combined then turn the heat down to low and simmer while stirring occasionally until the meat is browned, about 15 minutes.
Stir in the refried beans and the lime juice until well combined, then cook for a few more minutes until everything is warm. Taste and adjust seasonings. Remove from the heat.
To assemble the taco burgers, warm the buns. Top the bottom of each bun with ¼ of the filling, then top that with the shredded cheese. On each top bun, spread some guacamole, then add the lettuce and tomato. Serve warm, with pickled jalapeños on the side.