Place the shredded cabbage in a colander, adding a sprinkle of salt with each layer. Position the colander over a large bowl and let it stand for an hour. Afterward, rinse the cabbage lightly and pat it dry.

In a large bowl, toss together the prepared cabbage and carrots until evenly mixed.

In a small bowl, whisk together the buttermilk, milk, mayonnaise, vinegar, lemon juice, sugar, onion powder, salt, and pepper. Taste the dressing and adjust seasoning with more salt or pepper if needed.

Pour the dressing over the cabbage and carrot mixture. Toss everything until the vegetables are well-coated with the dressing.

Refrigerate the coleslaw for at least 2 hours, allowing flavors to meld, or store for up to 8 hours before serving and enjoying it.