Preheat the oven to 450 F.
Cut cabbage into 8 wedges.
Drizzle or brush olive oil on the wedges and sprinkle with salt, pepper, and amchur, if using. Use your hands to spread all of that into the cabbage. Bake for 25-30 minutes, flipping the wedges half way. The cabbage should be charred on the outside and tender!
While the cabbage roasts, make the curry leaf ranch. Mix milk and apple cider vinegar in a small bowl and set aside - this is the vegan buttermilk.
Heat olive oil in a small pan over medium heat. When the oil is hot, add the curry leaves. Stir frequently until it the leaves are darker and crisp, so about 3-4 minutes. Place the curry leaves in a small food processor and reserve any remaining olive oil to drizzle on the cabbage when it's out.
Add mayo, dijon mustard, nutritional yeast, salt, pepper, cilantro, and vegan buttermilk to the processor. Process until smooth and creamy. Taste and adjust if needed.
Drizzle the curry leaf ranch on the cabbage. Garnish with pistachios (or another nut) and cilantro.