Cut the steak into thin strips. Be sure to cut across the grain, as this makes the meat more tender!
Combine the marinade ingredients in a bowl. Add the sliced steak and stir to make sure sure all the meat has been coated. Put plastic wrap over the bowl and let the meat marinate in the fridge for 2 hours.
Slice the onion and pepper into thin strips.
Heat the olive oil in a skillet over medium-high heat. Cook the onion and pepper until the veggies start turning soft; they should get a little bit of char on them.
Add the garlic and green onions; cook for about 30 seconds to 1 minute, until the garlic becomes fragrant.
Set the vegetables aside on a plate.
Lightly spritz the same skillet with nonstick spray and cook the steak over medium-high heat, until the steak is no longer pink at all.
Add the vegetable mixture back to the skillet. Stir the steak and vegetables together until the vegetables have been well-coated with spices from the steak marinade.
Stack 8 flour tortillas on a microwaveable plate. Cover with plastic wrap or a damp paper towel and microwave for about 20 to 30 seconds until warm.
Spoon the steak-and-vegetable mixture into the warm tortillas. Top with shredded cheese, yogurt, salsa and herbs.