First, make the salad. Add the rice vinegar, brown sugar, sesame oil, gochujang, and salt to a medium bowl and whisk until the sugar is dissolved. Add the red pepper and green onions and toss to coat. Transfer to the refrigerator.
Next, whisk together the soy sauce, rice vinegar, sesame oil, garlic, brown sugar, fish sauce, gochujang, and ginger in a separate bowl. Set aside.
Heat a large skillet over medium/high heat. Add the ground beef and cook until almost fully cooked, 4-6 minutes.
Pour the soy sauce mixture over the beef and reduce the heat. Simmer for 3-4 minutes.
When the beef is cooked, move the beef to one side of the skillet and the sauce to the other. Sprinkle the cornstarch into the sauce and whisk vigorously until the cornstarch dissolves.
Stir the sauce and beef back together and gently simmer over medium heat until the sauce thickens.
Remove from the heat and top with sesame seeds and green onions.
Serve the beef alongside the red pepper salad and white rice.