Bring a large pot of water to a boil and cook the noodles according to package directions until just tender. Drain and set aside.
Heat 1 tablespoon of oil in a large skillet over medium-high heat. Add the ground beef and cook, breaking it up with a spoon, until browned and no longer pink. Drain excess fat if needed and transfer the beef to a plate.
Add the remaining tablespoon of oil to the same skillet. Add the sliced onion and cook for 2 minutes until it starts to soften. Stir in the garlic and cook for 30 seconds.
Add the shredded cabbage and black pepper. Cook, stirring often, for 4 to 5 minutes until the cabbage wilts but still has some bite.
Return the cooked beef to the skillet. Add the drained noodles and soy sauce. Toss everything together for 2 minutes until the noodles are coated and heated through.
Remove from heat and top with sliced green onions before serving.