Place the shredded cabbage in a colander set over a bowl and sprinkle with the salt. Massage and squeeze the cabbage with your hands to help it release its liquid and begin wilting. Set aside to drain for about 15 minutes.
Place the mayonnaise and lime juice in a large bowl and whisk to combine. Using your hands, squeeze the cabbage of its excess liquid one handful at a time and place in the bowl of dressing. Add the grated carrot, scallions, cilantro, jalapeño (if using), and garlic, and toss to combine. Taste and season with salt and pepper as needed.
