Squeeze the roasted garlic cloves into a blender (don’t include any of the papery skin). Add roasted onion wedges, roasted cabbage, soaked cashews, lemon zest, 1 ½ tablespoons lemon juice, 1 cup water, mustard, salt, and pepper. Blend on high until smooth and creamy. You may need to add a bit more water as you go to continue blending.