Tip : This is a 'do-ahead' kind of dinner, allow time for the steak to marinate and for the steak to 'dry' in the fridge. Don't forget to bring to room temperature before searing.
Mix together 3 tbsp soy sauce, 2 tbsp olive oil, 1 tbsp cumin and 1 tbsp chili powder reserving a couple of tablespoons full in a small bowl.
Combine marinade ingredients with a 12 inch piece of outside piece of skirt steak in a resealable plastic bag. If you cannot get an outside cut, which is a bit better, an inside cut will work as well.
Place in refrigerator for an hour, but up to 3 hours. Remove steak from bag and place on a rack over a sheet pan and return to refrigerate, uncovered. The idea is to 'dry' the steak. Keep in the refrigerator for a couple of hours, or overnight if you are not in a hurry.
Remove the steak from the refrigerator an hour before you are ready to prepare.
Heat a large skillet over high heat for about 2-3 minutes. Add room temperature steak and sear for about 4-5 minutes, then turn and sear for another 4-5 minutes,
Remove steak to a cutting board and allow to rest while you are cooking the vegetables.
Vegetables
Seed and slice one half of each of red, green and/or yellow bell pepper, peel and slice one medium Spanish onion.
Add a tablespoon of oil to the pan used to sear the steak, heat should be high or medium high.
Add onions and bell peppers and toss to combine.
When vegetables are done, about 4-5 minutes, slice steak into 1/2" strips and place on top of veggies.
Place 4 tortillas between two paper towels and heat on high for 30 seconds in a microwave oven.
Return heat under the skillet to high and pour reserved marinade around the outside of the skillet, this will cause the skillet to steam and sizzle (like in a restaurant!).
Garnish
Spoon a tablespoonful of sour cream in the center of each tortilla.
Add a portion of steak, peppers and onions, top with salsa.