Pound flank steak with a tenderizing mallet.

Marinate steak in soy sauce and water for 1 hour.

Grill steak until cooked to desired doneness.

Slice steak across the grain into thin strips.

Lay one tortilla in a large skillet.

Spread half of the shredded Jack cheese over the tortilla.

Top with half of the diced tomatoes, jalapenos, and chopped cilantro.

Add half of the sliced steak.

Cover with the second tortilla.

Cook on the stovetop until the bottom tortilla is toasted and golden brown.

Flip the quesadilla carefully.

Cook until the other side is toasted and the cheese is melted and gooey.

Remove the quesadilla from the pan.

Cut into sixths.

Serve immediately with salsa and sour cream.

Repeat the process for the remaining ingredients to make the second quesadilla.