In a small bowl, whisk together the tamari, toasted sesame oil, grated pear, minced garlic, grated ginger, sea salt, and black pepper.
Slice the flank steak against the grain into thin strips and place them in a shallow dish.
Pour the marinade over the beef, tossing to coat, and let it marinate for 20 minutes in the refrigerator.
Chop the red bell pepper and red onion into 1-inch chunks.
Thread the marinated beef strips onto skewers, alternating with the pepper and onion pieces.
Preheat a grill pan to medium-high heat and lightly coat with the avocado oil.
Grill the skewers for 3 to 4 minutes per side until the beef is cooked through and the vegetables have a smoky char.
Serve the skewers over the warm cooked brown rice and garnish with sesame seeds and sliced green onions.