Cook the Spaghetti: Bring a large pot of salted water to a boil. Cook the spaghetti according to package directions until al dente. Before draining, reserve about 1 cup of the pasta water, then drain the spaghetti.

Brown the Beef: While the pasta cooks, heat the avocado oil in a large skillet or Dutch oven over medium-high heat. Add the ground beef and chopped onion, breaking the meat apart with a spoon. Cook until the beef is browned and the onion is soft, about 5-7 minutes. Drain any excess grease.

Add Aromatics: Add the minced garlic and ginger to the skillet and cook for another minute until fragrant.

Make the Sauce: In a small bowl, whisk together the soy sauce, brown sugar, rice vinegar, sesame oil, cornstarch, and red pepper flakes (if using).

Combine and Thicken: Pour the sauce mixture over the ground beef. Stir continuously and cook for 1-2 minutes, until the sauce begins to bubble and thicken.

Finish the Dish: Add the drained spaghetti to the skillet with the beef and sauce. Toss everything together until the noodles are fully coated. If the sauce is too thick, add a splash of the reserved pasta water to reach your desired consistency.

Serve: Divide the Asian Ground Beef Spaghetti among bowls and garnish with sliced green onions and toasted sesame seeds before serving.