In a non-metal bowl, combine avocado, tomato, onion and cilantro. Gently mix ingredients and season to taste. Cover and refrigerate until ready to use.
In a large frying pan over medium heat, bring the peanut oil to 350 degrees F. While the oil is heating, line a baking tray with paper towels. Once the oil is hot, use tongs to gently place a tortilla into the hot oil for about two or three seconds, turn once and remove to the paper towel-lined pan. Do this with all the tortillas. The goal is to soften the tortillas a bit; do not overcook or they’ll become brittle.
Assemble taquitos by placing strips of yellowtail across the tortilla; roll tightly and secure each taquito with a toothpick.
Fry taquitos until crisp, about 3-4 minutes on each side. Remove to paper towel-lined pan and let cool just a bit, then arrange over a bed of avocado salsa, garnish with sour cream or Mexican crema and enjoy.