Instructions

1. 1

   Season the steak with salt and pepper on both sides.

2. 2

   Heat 1 tablespoon of olive oil in a pan over high heat until it's almost smoking, then sear the steak on each side for 1 minute. Reduce the heat to low and cook the steak until desired doneness.

3. 3

   Remove from heat and let sit for 10 minutes. Slice the steak into strips.

4. 4

   Using the same pan, heat 1 1/2 tablespoons of olive oil over medium heat.

5. 5

   Add the onion and thyme and saute for 10 minutes, until the onions are caramelized, stirring occasionally.

6. 6

   Whisk mayo, mustards, sour cream, and salt into a bowl and set aside.

7. 7

   To assemble the sandwiches, spread a tablespoon of mayo sauce on each side of the roll.

8. 8

   Place a layer the steak strips on top of the mayo, sprinkle with salt and pepper, and top with the caramelized onion rings.

9. 9

   Place the baby arugula on top of the onion rings, and cover the sandwiches with the top half of the buns.