Wash and dry the vegetables. 

Prepare the cabbage. Slice the cabbage into quarters, slicing from top to bottom. Then cut the core out of each quarter. Slice each cabbage wedge crosswise or lengthwise into thin strips. 

Prepare the onions. To thinly slice the red and white onions, cut along the lines of longitude from to bottom. 

Prepare the carrots. Cut off the top and bottom tip and remove the skins of the carrots using a vegetable peeler. If you don't have a vegetable peeler, you can use a knife instead. Use it with caution. 

Prepare the kale. Fold the leaves of the kale together and hold them. Then use a knife to cut off the stalk. After that, roll up the kale leaves and cut the kale into slices. 

Now, your veggies are ready. It's time to mix them up. Add the cabbage, red onion, white onion, carrots, and kale leaves to a large glass bowl and toss to combine. Season with salt and pepper and set aside.

Then add the vinegar and sugar to a small saucepan set to medium-high heat. Stir the mixture until the sugar thoroughly dissolves. Remove from heat and whisk in the vegetable oil, mustard, and celery seeds to create the dressing. While still warm, pour over the cabbage mixture and toss to combine thoroughly. 

Cover it with plastic wrap and let it chill in the refrigerator for a couple of hours before serving. You can season with additional salt and pepper before serving too.