While the steak is chilling, whisk tamari, curry paste, hoisin, vinegar, brown sugar, beef stock and 3 teaspoons cornstarch. Set aside.
Heat a large non-stick skillet to a high heat. Add peppers and onions. Stir-fry veggies until softened, about five minutes. Make sure to use tongs to toss the veggies every 30 seconds or so they don't burn. (It's ok if they get a little charred.)
While the pepper cook, , use a very sharp knife to slice the steak into very thin pieces. Season with salt and pepper. Add to a bowl and toss with remaining cornstarch.
Once the veggies are done, wipe pan clean and place over a high heat again. Add two teaspoon canola oil. Once the oil is hot, add half of the beef. Fry until brown, crispy and cooked through. Remove from the pan and repeat with other half of the beef.
Add the cooked beef, pepper and sauce to the pan. Toss, bring to a boil and then reduce to a simmer until thickened, about 1-2 minutes. Season with salt and pepper. Serve over rice and garnish with chopped cilantro.