Combine all the marinade ingredients in a blender. Start at low speed and increase to high, blending for 1 minute, until the mixture turns smooth. Add the sliced steak and marinade into a big bowl. Toss to mix well. Marinate at room temperature for 30 to 60 minutes, or refrigerate covered, up to overnight.

Prepare the roasted squash and coleslaw while marinating the beef.

Drain the steak with a colander and discard the marinade. Transfer the steak into a big bowl. Add 1 tablespoon sesame oil and cornstarch. Toss with a pair of tongs or with your hand until the steak is evenly covered with cornstarch.

Heat the remaining 1 tablespoon of sesame oil in a large skillet and heat over medium high heat until hot. Cook the beef in batches. Spread one third of the beef into a single layer with minimal overlapping. Cook without touching for 30 seconds or so. Shake the pan gently and continue cooking until the bottom turns golden brown. Flip to cook the other side, until golden brown. Transfer the beef to a plate immediately. Cook the remaining batches using the same method. Add more oil if needed. Turn to medium heat if the pan starts to smoke too much.

Once you've cooked all the beef, add the onion to the skillet. Sprinkle a pinch of salt over the onion. Cook and stir until the onion turns tender. Add the onion to the beef and toss to mix well.

Serve hot as a main course over steamed rice or noodles with roasted squash and coleslaw on the side (see recipes below). Or you can assemble it in meal-prep containers and store it in the fridge for up to 4 days.