Heat a large cast-iron skillet over high heat. Add cabbage and Brussels sprouts; cook, turning occasionally, until charred on all sides, about 5 minutes. Let cool for 1 minute. Thinly slice cabbage and Brussels sprouts.
In a small bowl, whisk together orange juice, lemon juice, dill, mustard, salt, and pepper. Whisk in oil in a slow, steady stream until smooth.
In a large bowl, stir together cabbage mixture, red onion, and dressing. Garnish with dill, if desired.
Recipe by Paula Deen Magazine at https://pauladeenmagazine.com/charred-cabbage-brussels-sprouts-slaw/