Mix garlic, grated onion, grated ginger, toasted sesame oil, and brown sugar together in a mixing bowl. Stir in grated pear, soy sauce, and red pepper flakes.

Transfer meat to marinade and toss to coat on all sides. Cover and refrigerate, 1 to 2 hours.

Season meat with salt and a drizzle of vegetable oil. Toss.

Brush a cast iron skillet with a little vegetable oil and place over high heat. When the skillet is very hot, add beef in a single layer and cook until meat begins to caramelize around the edges and moisture begins to evaporate, 2 to 3 minutes per side. Serve over hot rice and top with green onion slices.