Make the sauce by adding all the ingredients (coconut aminos, water, rice wine vinegar, ginger, garlic, sesame oil and salt) to a blender and blending until totally smooth, with no visible bits of ginger or garlic. Set aside.
Pat the steak dry with paper towels and trim any fat. Thinly slice against the grain (meaning, if you see the lines/fibers in the steak running in one direction, slice the steak against those lines, not along those lines).
Heat 2 tablespoons of oil in the skillet over high heat. Add the steak and spread out into an even layer. Sprinkle with ½ teaspoon salt and let the steak cook, flipping once or twice, until brown on both sides, about 8 minutes total. The pan might get full of frothy liquid but that's fine, we're not looking for a dark sear. Turn off the heat and remove the steak to a medium bowl. Drain the greasy liquid into a small bowl (see notes.) Wipe the pan carefully (it doesn't have to be totally clean or dry).
While the steak is cooking, peel, halve and thinly slice the onion.
Place the pan back over high heat. Add 1 tablespoon oil and then add the onions and ¼ teaspoon salt. Cook, stirring occasionally, until soft and transparent, about 8 minutes.
Add the sugar snap peas and carrots and cook, stirring occasionally, until tender, about 5 minutes.
Add the steak and any juices accumulated in the bowl. Add the sauce and stir everything together. Let the sauce simmer and thicken, stirring occasionally to make sure everything is coated with the sauce, about 2-3 minutes. Garnish with the toasted sesame seeds and sliced scallions and serve over cauliflower rice.