Cut the carrot into 2-inch chunks and add to your Thermomix bowl. Process at speed 5 for 4 seconds until finely shredded. Add the cabbage pieces (already cut into 2-inch chunks as noted) to the bowl with the shredded carrot. Process at speed 4 for 4 seconds, stirring through the lid opening to ensure even shredding. I find that stirring during processing helps the vegetables move around the blade for consistent texture.

Add the mayo, apple cider vinegar, sugar, Dijon mustard, salt, black pepper, and celery seed directly to the bowl with the shredded vegetables. Process at speed 4 for 4 seconds while stirring through the lid to distribute the dressing evenly. Scrape down the sides and bottom of the bowl with a spatula, then process again at speed 4 for 4 seconds while stirring to ensure every strand of vegetable is coated. I like to use Hellmann's mayo specifically because it creates the creamiest, most cohesive coleslaw texture.

Transfer the finished coleslaw from the Thermomix bowl to a serving bowl. The coleslaw is ready to serve immediately, or you can refrigerate it for a few hours to let the flavors meld together.