2 6oz pieces lean filet mignon Half of a 1oz package fajita seasoning Cooking spray 1 large Vidalia onion, sliced thin 1 large green bell pepper, seeded and sliced thin 1/2 ripe Hass avocado, peeled 1 cup store-bought fresh salsa 1/2 cup chopped fresh cilantro 8 6-inch low-carb, high fiber tortillas 1/2 cup nonfat Greek yogurt

Heat a grill pan over high heat.
Season the steaks with half of the fajita seasoning, and spray them lighly with cooking spray. When the grill pan is hot, add the steaks and grill them for 3 minutes per side for medium-rare. Transfer the steaks to a platter, cover them with foil, and set them aside to rest. (Leave the grill pan on the heat.)
Combine the onion and pepper in a large bowl, and spray them lightly with cooking spray. Season the vegetables with the remaining fajita seasoning, and place them on the grill pan. Grill the vegetables until they are charred and crisp-tender, about 7 minutes. Transfer the vegetables to a bowl, and cover it with foil to keep them warm.
While the vegetables are grilling, mash the avocado lightly with a fork in a medium bowl. Stir in 1/4 cup of the salsa and half of the cilantro to make the guacamole.
Holding them with flameproof tongs, char the tortillas on each side over an open flame. (Or toast them under the broiler.) Place the tortillas on a plate, and cover them with a towel to keep them warm.
Cut the steaks into thin slices.
To assemble the fajitas, spoon some of the guacamole onto each tortilla. Pile the steak and the pepper-onion mixture on top of the guacamole. Top with the yogurt, remaining 3/4 cup salsa, and remaining 1/4 cup cilantro. Serve.