In a medium bowl, add in the cubed steak, olive oil, soy sauce, garlic, lemon juice, salt, paprika, garlic powder, onion powder and toss together to coat. Refrigerate for 30 minutes or overnight.
Preheat oven to 375℉.
Assembly:
Heat the olive oil in a large skillet over medium heat. Sauté the onions and peppers on low heat for 5-6 minutes or until soften. Season with salt to taste. Transfer vegetables to a plate and set aside.
To the same skillet, turn up the heat to medium high and add in the steak pieces - cook for 2 minutes per side. Then, add in onions, peppers, 1/2 cup shredded cheese and mix everything together. Remove skillet from heat source.
Lightly brush one side of the tortillas with olive oil and on the unbrushed side, fill them with about 1/4 cup of the steak and pepper mixture. Layer them in the pan as shown in the photos above. You can use a small shot glass to keep the filled ones upright as you fill the rest. Repeat until you're done and all the mixture is used up. Evenly sprinkle tacos with remaining 1 cup shredded cheese. Bake 15-18 minutes or until the cheese is melted and slightly golden.
Avocado Sauce:
While the tacos are baking in the oven. In a mini food processor, pulse together the avocados, sour cream, garlic, lemon, parsley, salt, onion powder, olive oil and milk until smooth. Taste and adjust seasonings and consistency if needed. Add more milk to make the consistency more runny.