Add thinly sliced Grass Run Farms 100% grass fed flank steak. Season with salt.
Cook until browned and desired doneness is reached, about four minutes or when internal temperature reaches 145°F. Remove from skillet.
Melt butter in skillet and sauté green peppers and onions until softened. Remove from skillet.
Spread mayo on one side of each slice of sourdough bread.
Heat griddle on medium-high heat.
Place four slices of bread mayo-side down on griddle surface.
Add one slice of provolone, one slice of pepper jack, ¼ of cooked Grass Run Farms flank steak, ¼ of the cooked peppers and onions, a second slice of provolone, a second slice of pepper jack, and top with the second slice of bread mayo-side up. Repeat for all four sandwiches.
Flip sandwiches once bottom bread is toasted.
Cook until sandwiches are evenly toasted, and cheese is melted.