Brown the meat in a large frying pan, season with salt and pepper. Remove the meat from the pan and set aside.
fry the onions and garlic in the pan til the onions soften. 3-5 minutes or so. Add the tomato sauce and cumin, and return the beef to the pan. Stir to combine. Simmer another 5-8 minutes.
Fill a medium skillet with about 1/3" of oil. Heat oil to crackling.
Build each taquito by making a line of ingredients (meat, sour cream, guac, salsa, cheese) down the center of each tortilla shell, then roll tightly to be about 2" wide. Using a pair of tongs place the taquito seam side down into the oil for about 10 seconds til browned. Turn and fry the top side. Repeat with rest of taquitos.