
Heat the oil in a medium skillet over medium-high heat. Add the onions and cook for 3 minutes, then add the ground beef and cook for 6 to 8 minutes, breaking up the meat into small pieces as it cooks. Drain and discard any excess grease if necessary.
Add the taco seasoning and tomato paste. Stir together until fully combined. Cook for 1 more minute. Remove the skillet from the heat and stir in the lime juice. Set aside.
Assemble the crunchwraps by adding 3-4 heaping tablespoons of the ground beef filling into the center of the tortilla and top with 2 tablespoons of nacho cheese. Spread 1 ½ tablespoons of sour cream onto the tostada shell and place it on top of the meat and cheese mixture. Add 1 ½ tablespoons each of shredded lettuce and diced tomatoes on top of the tostada.
Fold the bottom of the tortilla over the top of your fillings towards the center. Working clockwise, turn the crunchwrap and continue folding, anchoring the folded part closed with your other hand and pleating the tortilla like you are wrapping a present. Repeat until the tortilla encloses the filling.
Melt 1 tablespoon of salted butter in a large skillet over medium heat and add the crunchwrap seam side down. Lightly press on it with a spatula to help it toast evenly and seal the folds. Toast for 2 minutes or until golden brown.
Flip the crunchwrap supreme and continue toasting for an additional 2 minutes or until golden brown.
Repeat this process with the remaining wraps and butter. Serve immediately with guacamole, sour cream, or hot sauce.