Combine the rice and water in a medium saucepan. Bring to a boil, then reduce heat to low, cover, and cook for 18 minutes until the rice is tender. Remove from heat and let it rest covered for 5 minutes.
Heat 1 tablespoon of sesame oil in a large skillet over medium-high heat. Add the ground beef and cook until browned, breaking it up with a spoon as it cooks. Season with salt and pepper.
Add the sliced onion and minced garlic to the skillet. Cook for 2 minutes until the onion starts to soften.
Stir in the shredded cabbage and soy sauce. Cook for 5 to 7 minutes, stirring often, until the cabbage wilts but still has some bite.
Fluff the rice and stir in the remaining tablespoon of sesame oil along with the sesame seeds. Spoon the beef and cabbage mixture over the rice to serve.