For Marinade: Preheat your waffle iron on medium. In a zip-top plastic bag or bowl, combine the lime juice, oil, cumin, and salt and pepper. Add the flank steak and allow it to marinate while you prepare the rest of the ingredients.
For Vegetables: In a medium bowl, toss the vegetables with the salt. When the waffle iron has preheated, coat both sides of the grid with nonstick spray, place as many vegetables as will fit in a single layer on the waffle iron and close the lid. Cook the vegetables about 2 minutes, or until they are just starting to soften and display waffle marks.
Repeat as necessary with remaining vegetables, removing the finished vegetables to a covered bowl to keep them warm.
For Tortillas: In a medium bowl using your hands, combine the Maseca, water and salt and knead until a soft dough forms. It should be about the consistency of Play-Doh.
Divide the dough into six roughly equal pieces and roll those pieces into balls. Place the balls on a towel and cover with a damp towel to keep them from drying out.
Press one ball into a disc with your hand. Place the disc on a sheet of plastic wrap covered with Maseca and cover that with another sheet of plastic wrap. Using a rolling pin, roll out the dough into a circle about 6 inches across.
Place the dough into the waffle iron, close the lid, and cook for about 1 minute or until the dough has firmed up to a tortilla consistency and bears light waffle marks.
While the first tortilla cooks, prepare another ball of dough. Remove the finished tortillas to a tortilla warmer or wrap them in a clean kitchen towel to keep warm.
For Beef: When the last tortilla has finished waffling, place the flank steak in the waffle iron and close the lid.
Cook the steak for about 5 minutes. Thicker cuts may take longer. You want it to reach an internal temperature of about 140 degrees. Use an instant-read thermometer or cut into the steak. You should see some pink — but no red — in the center.
Remove the finished steak to a cutting board, turn off the waffle iron, and let the meat rest for a couple of minutes before slicing it thinly against the grain.
To Assemble: If the tortillas have cooled too much, place one in the waffle iron for 10 seconds and let the residual heat warm it up. Pile the sliced meat into a waffled tortilla and add waffled vegetables.