Prepare the vegetables. Add the red peppers, carrots, rice vinegar, salt, sesame oil, and lime juice to a bowl and toss. Place in 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.
Remove the vegetables from the refrigerator and add the green onions and cilantro to the vegetables, toss.
Build the lettuce wraps by filling each ground beef and top with vegetables. Garnish with sesame seeds and enjoy.