Bring a large pot of salted water to a boil. Cook noodles 1 minute shorter than the package directions. Reserve about ½ cup of the cooking water and drain. Set aside.

In a large skillet, heat the oil over medium-high heat. Add the white parts of the green onions and cook for about 1 minute. Add the garlic and cook for 30 seconds. Add peanut butter, gluten-free gochujang, and seasoned rice vinegar to the skillet. Gradually whisk in the reserved hot noodle water until the sauce is creamy and glossy. Add salt and pepper to taste.

Add the cooked noodles to the skillet. Toss until every strand is coated in the spicy-peanut sauce. Top with the reserved green onion tops and serve.