Step 1

Prepare all the ingredients before cooking. Make sure the flap steak is cut into thin strips, and slice the bell peppers and onions into thin strips as well.

Step 2

Season the steak generously with Thundering Longhorn Beef Rub or your preferred beef seasoning. Rub the seasoning into the meat using your hands, making sure it's evenly distributed.

Step 3

Cut the ciabatta buns in half and set them aside.

Step 4

Preheat a griddle or large skillet over high heat. You want the griddle to be hot before adding the ingredients.

Step 5

Once the griddle is hot, add the sliced bell peppers and onions to the griddle. Sauté them for about 5 minutes until they are slightly softened but still have a bit of crunch to them. You don't want them to be too soft.

Step 6

Season the veggies with salt and pepper to taste. Remove them from the griddle and set them aside on a plate or in a bowl.

Step 7

Add the seasoned flap steak to the griddle and cook it for about 2-3 minutes on each side until it's nicely seared. You want the steak to be browned and slightly crispy on the outside, but still juicy and tender on the inside.

Step 8

Once the steak is seared, add the sautéed veggies back onto the griddle with the steak. Mix everything together for a few minutes to allow the flavors to meld together.

Step 9

Divide the steak and veggie mixture into 4 equal piles on the griddle. Each pile should be big enough to fit on a ciabatta bun.

Step 10

Top each pile with 3 slices of Pepper Jack cheese. Allow the cheese to melt over the steak and veggies for about 1-2 minutes.

Step 11

While the cheese is melting, toast the ciabatta buns. You can do this on the griddle or in a toaster oven.

Step 12

To assemble each sandwich, spread a generous amount of mayo on the bottom half of each bun. You can use regular mayo or flavored mayo if you prefer.

Step 13

Add a pile of the steak and veggie mixture on top of the mayo. Make sure to include some of the melted cheese in each sandwich.

Step 14

Finish each sandwich with a generous spoonful of guacamole salsa on top of the steak mixture.

Step 15

Top each sandwich with the other half of the ciabatta bun, and serve hot.