In a large skillet over medium-high heat, add the ground beef. Cook until browned, breaking it apart with a spatula, about 5-7 minutes. Drain excess fat if necessary.
Stir in the soy sauce, sesame oil, gochujang, minced garlic, grated ginger, erythritol, and rice vinegar. Cook for another 3-5 minutes until the sauce thickens slightly. Season with salt and pepper to taste.
While the beef is cooking, prepare the cucumber salad. In a bowl, combine the sliced cucumber, green onions, and sesame seeds. Toss gently to mix.
Serve the spicy beef over a bed of cucumber salad. Garnish with additional sesame seeds and green onions if desired.