In a large skillet over medium heat, add the avocado oil. Once hot, add the diced onion and sauté for 2-3 minutes until translucent.
Add the ground beef to the skillet. Cook, breaking it apart, until browned and cooked through.
Drain excess fat if needed. Add taco seasoning and water. Stir to combine and simmer for about 5 minutes until water evaporates.
Remove from heat and let the beef mixture cool slightly.
Warm the corn tortillas by wrapping in a clean kitchen towel and microwaving for 30 seconds or warming on a skillet to keep them pliable.
Spoon about 2 tablespoons of beef mixture onto one end of each tortilla. Sprinkle cheese over beef and roll tightly. Secure with toothpick if desired.
Heat oil in a frying pan or deep fryer over medium-high heat. Fry taquitos seam side down in batches for 3-4 minutes until golden and crispy.
Remove taquitos with slotted spoon and drain on paper towels.
Serve taquitos topped with shredded lettuce, diced tomatoes, sour cream, salsa, and guacamole.