Rinse the red cabbage and kale under cold water. Remove any tough stems from the kale and thinly slice the leaves. Thinly slice the red cabbage, grate the carrots, thinly slice the red bell pepper, and thinly slice the green onions. Place all vegetables in a large mixing bowl.
In a small bowl, whisk together rice vinegar, soy sauce, honey or maple syrup, sesame oil, freshly grated ginger, minced garlic, and sriracha sauce. Season with salt and pepper to taste.
Pour the dressing over the prepared vegetables in the mixing bowl.
Toss the vegetables and dressing together until well combined, ensuring all the vegetables are evenly coated with the dressing.
Cover the bowl with plastic wrap or transfer the slaw to an airtight container. Refrigerate for at least 30 minutes to allow the flavors to meld together and the vegetables to slightly soften.
Before serving, sprinkle toasted sesame seeds over the slaw for added crunch and flavor. Serve chilled.