Cut the avocado from top to bottom and twist each half to expose the pit. Carefully wedge a knife into the avocado pit and twist it to pop it out (or scoop it out with a spoon). With a butter knife, score the inside of each half into small, diced pieces. Scoop out the diced avocado using a spoon and set aside until plating. Wash the bell pepper, then cut into 1/4-inch strips. Cut the onion into 1/4-inch slices. Place a large sauté pan over medium-high heat, add 1 tablespoon of oil, and preheat for 2–3 minutes. Carefully place the cut vegetables into the pan. Sauté for 3–4 minutes to begin browning and softening.
Now, add the marinated fajita strips to the pan. Cook for 3–5 minutes until the steak is browned and reaches a safe internal temperature of 145°F and allow to rest for at least 3 minutes. Taste, then add salt, pepper, or your favorite hot sauce, as desired.
As the steak cooks, place the second sauté pan on medium heat. Add 1–2 teaspoons of oil. Place 2–3 flour tortillas into the pan to warm and soften, flipping after 1–2 minutes. Hold warm in a clean kitchen towel. Turn off all heating elements.
To assemble your fajitas, spread crema down the middle of the tortillas. Add the beef mixture, salsa verde, shredded cheese, and diced avocado. Fold the tortillas in half, and enjoy!