Trim off the limes' tops and tails using a small paring knife. Section the lime using the technique shown here. Cut each section into thirds. Place them in a small bowl, sprinkle with a little salt, drizzle with 1 tablespoon of olive oil, stir and set aside.
Cut the butternut squash in half lengthways, scoop out the seeds and discard, Cut each half, top to bottom, into 1 cm thick slices and lay them out on a large baking sheet lined with parchment paper.
Place the cardamom pods in a mortar and use the pestle to get the seeds out of the pods. Discard the pods and pound the seeds into a rough powder. Transfer to a small bowl, add the allspice and the remaining 3 tablespoons of oil, mix and brush over the butternut slices. Sprinkle with sea salt and place in the oven for 15 minutes or until fork-tender. Remove from the oven and set aside to cool. Peel off the skin or leave it on if you prefer.
Whisk together the yogurt, tahini, lime juice, 2 tablespoons of water and a pinch of salt. The dressing should be thick but runny enough to pour; add more water if necessary.
To serve, arrange the cooled butternut slices on a serving platter and drizzle with the yogurt dressing. Spoon over the lime pieces and their juices and scatter the chilli slices on top. Garnish with the coriander or chives and serve.