Finally, assemble the crunchwraps. Start preheating a cast iron griddle or frying pan over medium-low heat so it's ready to crisp the crunchwraps once they're assembled.
Next, warm the flour tortillas between dampened paper towels in the microwave for about 30 seconds each, until they're soft and pliable. Then, lay the tortillas flat on your workspace.
Spoon about a half cup of beef into the center of each tortilla, and gently spread the beef into a single layer, roughly 6 inches in diameter. Next, drizzle about 1 tablespoon of the nacho cheese sauce over the beef. Add a tostada on top of the beef and cheese, then add a layer of shredded lettuce, followed by diced tomato. Finally, dollop about 1 tablespoon of sour cream (or Greek yogurt) on top of the lettuce and tomato.
Next, wrap the crunchwraps in a six-sided fold. First, take opposite sides and fold them in to meet in the center. Then, hold this in place with your fingers while sliding your thumbs under the near side of the tortilla. Push the tortilla in towards the center, letting it crease naturally in the space between your thumbs. You should be able to push the tortilla at a slight angle with both thumbs, letting one side fold in just before the other, so the tortilla lays flat in the center. Repeat this on the other side to close the crunchwrap completely.
Finally, toast the crunchwraps on the preheated griddle. Carefully place them seam side down on the pan and cook over medium-low heat until crispy and golden brown on the bottom, about 4 to 5 minutes. (Toasting this side first should help your crunchwrap stay closed). Then, carefully flip the crunchwraps and toast the other side until crispy and golden brown, another 4 to 5 minutes.
Transfer crunchwraps to a cutting board and slice in half. Serve immediately.