Prep all ingredients for Bearnaise Sauce before starting to cook steak.
Rub each steak with salt and pepper.
Coat a grill pan with cooking spray; set over medium high heat.
Place steak on pan and cook, without turning, for 5 minutes.
Flip steak, cook about 4-6 minutes for medium doneness.
Remove steak to a cutting board and loosely cover with aluminum foil. Let rest for at least 10 minutes.
To make sauce, bring a small saucepan one-third filled with water to a boil. In a metal bowl, beat egg yolk with 1 Tbsp. water (at room temperature) until frothy.
Set bowl over saucepan (wear oven mitts) and cook, stirring constantly for about 3-5 minutes until yolk thickens.
Remove egg yolk from heat; slowly whisk in melted butter. Combine well.
Stir in lemon juice, remaining salt and pepper, and fresh herbs.
Serve steak with sauce.
One steak and 1 Tbsp. sauce per person.