How to Make It
Cut each of the cabbages in half. Save the other half of each color for another purpose. Cut each cabbage half into quarters. Remove the small triangle of the core in each of the quarters. Take each of the quarters and finely shred the cabbage by running your knife across the width of the cabbage in very fine slices. Place all shredded cabbage into a medium bowl.
Cut the red onion in half from stem to tip. Peel and stem the onion. With the cut side down and working from right to left, cutting along the natural lines of the onion, make angled cuts into the onion. Space your cuts closely together to make really thin moon shaped slices. Place the onion in the same bowl as the cabbage.
Make the dressing by measuring out the yogurt dressing and Sriracha into a standard measuring cup. Add a few grinds of pepper.
Pour the mixed dressing over the salad. Mix the salad well and set aside in the refrigerator for several hours.
When you are ready to serve, give the salad another toss and add the toasted seeds, the chopped cilantro and serve. You can sprinkle additional sunflower seeds on the top of the salad before serving.