Combine the soy sauce, brown sugar, green onions, sesame oil, grated pear, grated ginger, minced garlic, and sriracha together in a bowl.
Whisk the mixture very well then pour 1/3 cup in a separate container; cover and set aside for serving.
Add the beef to the marinade in the bowl and toss to coat evenly.
Cover and refrigerate for 1-24 hours (I marinated for 5 hours).
Remove the meat from the refrigerator 30 minutes prior to cooking.
Prepare the rice, per package instructions.
Heat a grill pan over medium-high heat.
Coat with cooking spray then place some of the beef in the grill pan making sure not to crowd the pan.
Cook for 1-2 minutes then flip and cook for an additional 1-2 minutes.
Remove from the grill pan and place onto a serving plate and cover loosely with a tin foil tent.
Cook the remaining beef.
To serve, spoon some rice into the center of the lettuce leaf then top with some beef followed by some toasted sesame seeds.
Serve with additional reserved marinade and sriracha, if desired. Enjoy.