Combine garlic, jalapeno, cumin, cilantro, lime juice, sugar and oil in a mixing bowl. Whisk until well combined and transfer to a plastic gallon-size zip top bag, add flank steak and marinate under refrigeration for 1 to 4 hours.
Assemble tomatoes, cheese and lettuce leaves on a platter.
Preheat grill to medium-high heat and place 8-inch cast iron pan directly on the grill or over side burner set to medium-high heat.
Remove steak from marinade, pat dry and season with salt and pepper as desired. Grill steak for 6 to 8 minutes per side or to desired doneness. Remove and allow steak to rest 5 minutes before slicing into 1/2-inch thick slices.
Meanwhile, coat preheated cast iron pan with non-stick spray. Add corn, red onion and poblano peppers; saute for 6 to 8 minutes or until corn has nice char marks and peppers are tender crisp. At the same time, coat Mission(R) Soft Taco Flour Tortillas with non-stick spray and grill on each side no more than 30 seconds.
Immediately place sliced steak on top of corn mixture in cast iron pan and serve sizzling hot.
Substitute chicken in place of flank steak for a non-red meat variation.
Drizzle your favorite salsa and sour cream if desired.