Preheat panini grill to 450° or conventional oven to 400°

Combine water, vinegar, sugar, and salt in a small saucepan. Heat on high and stir to dissolve. Add red onions. Boil for one minute, and remove from heat. These are super quick pickled red onions.

Combine mayo and steakhouse seasoning. Set aside.

Assemble the sandwich in this order. Mayonnaise on the bottom, roast beef, roasted peppers, cheese, onions, and then mustard on the roll.

Spray panini grill with non-stick spray or vegetable oil. Lightly spray sandwich with non-stick spray or put a tiny bit of oil on the top bun.

Move only once to get the grill marks. To make perfect marks, visually pick a spot on the sandwich and point it to "10 o'clock". Move that same visual point to "2 o'clock". Just like hands on a steering wheel.

Variations; Horseradish/honey/dijon mustard, shaved red onion, arugala, spinach, watercress, aioli, egg, cheddar, bacon, sourdough