Cut cabbage and carrot into thin strips. Mix together in a large bowl and set aside.

Cut into vanilla bean lengthwise to open it, then scrape out the seeds.

In a smaller bowl, combine mayonnaise, white vinegar, lemon juice, sugar, poppy seeds, vanilla bean seeds, salt and pepper. Whisk them together until the sauce becomes nice and smooth. 

Pour the sauce into the bowl with the cabbage and carrot. Toss together until well combined. You may eat right away, however, I recommend covering and storing it in the fridge for at least a couple hours for the cabbage to soften and flavours to fully merge together.