Preheat a 2-burner cast-iron grill or two grill pans over medium-high heat for about 3 minutes.
Drizzle the grapeseed oil over the steaks and sprinkle with salt. Place the steaks on the grill, seasoned-side down, and cook for 4 to 5 minutes per side, or to the desired doneness.
Place the broccoli spears on the grill next to the steaks and cook for 4 minutes per side. Brush the steaks with some teriyaki glaze just before taking them off the grill. Let the steaks rest for about 8 minutes before slicing.
Arrange the sliced steak and grilled broccoli on a serving platter and finish with additional teriyaki glaze. Sprinkle with toasted sesame seeds and garnish with several sprigs of cilantro.
Combine the pineapple juice, soy sauce, scallions, brown sugar, ginger, garlic and sesame oil in a medium saucepan. Bring to a boil, then reduce the heat to a simmer. Cook until thick, about 20 minutes.