Whisk together all the ingredients for the salmon marinade. Place the salmon, skin-side up, in the marinade and let sit in the refrigerator for 30 minutes-4 hours. Preheat the oven to 400F. Pour off the marinade, flip the salmon then bake the salmon for 15 minutes (about 10 minutes per inch thick). Once cooked, remove the skin.
Meanwhile, cook the soba noodles in boiling water for 2-4 minutes. (Don't overcook - check them at 2 minutes.) Rinse with cool water to stop the cooking. You may need to rinse the noodles again to get them to loosen up if they sit for a bit while you make the stir-fry.
Whisk together the ingredients for the stir-fry sauce, set aside.
In a large skillet, heat the coconut oil over medium heat. Add the ginger, garlic, and scallions. Cook for 1 minute until fragrant, then add the mushrooms. Cook for 2-3 minutes then add the red pepper. Cook for another 3-4 minutes then add the noodles and cabbage. Add the stir-fry sauce and toss to combine, using tongs if needed. Cook until the noodles are hot and the cabbage is slightly wilted.