Meanwhile, sauté the onion with the olive oil in a skillet over medium-high heat. Cook, stirring fairly often, until the onion is very lightly browned (approx. 6-8 minutes).
Just before you're ready to add the meat to the pan, add the ramen noodles to the boiling water (they will only take around 3 minutes).
Add the steak to the skillet and cook it for a couple of minutes, stirring often, until it's as cooked as you'd like it (I prefer medium to medium-rare, so it does not need long).
Add the sauce ingredients to the skillet and give it a good stir. I add them right into the pan, so it's best to have them ready to go so you don't overcook the steak. You may want to reduce the heat if the sauce is bubbling too much.
Drain the ramen noodles and add them to the skillet. Toss until everything is nicely coated, and serve immediately.