Begin by thinly slicing the beef sirloin against the grain for tenderness. Mince the garlic and slice the onion and red bell pepper into thin strips. Cook the noodles according to the package instructions until al dente, then drain and set aside.

In a large skillet or wok, pour in 2 tablespoons of vegetable oil and heat it over medium-high heat. You’ll know it’s ready when the oil shimmers.

Add the sliced beef to the skillet in a single layer, cooking for about 3-4 minutes without stirring. Flip the beef once it’s browned, then remove it from the skillet and set it aside.

In the same skillet, add the minced garlic and sliced onion, stirring for about 2-3 minutes until they become fragrant and translucent.

Now stir in the sliced red bell pepper, cooking for an additional 2-3 minutes until they’re slightly tender.

In a separate bowl, whisk together the soy sauce, brown sugar, gochujang, sesame oil, and rice vinegar for the sauce.

Pour the prepared sauce mixture into the skillet with the sautéed vegetables. Stir well to evenly coat the veggies.

Return the cooked beef to the skillet and toss it with the vegetable mixture, ensuring everything is well-coated in the sauce.

Introduce the cooked noodles into the skillet, tossing everything together until the noodles are fully coated in the sauce.

Continue cooking everything together for another 2-3 minutes until the noodles are heated through.

Once cooked, remove the skillet from heat and dish out the Korean Gochujang Beef Noodles to serving plates. Garnish generously with sesame seeds and sliced green onions.