Preheat your oven to 400°F (200°C). Using a sharp knife, halve the medium kabocha squash and scoop out the seeds with a spoon. Leave the skin on as it softens during roasting and is edible.
In a mixing bowl, whisk together 2 tablespoons of miso paste, 2 tablespoons of olive oil, and a pinch of salt and pepper to make the glaze.
Place the kabocha halves cut-side up on a baking sheet and brush the miso mixture generously over the flesh.
Roast in the preheated oven for 35-40 minutes, until the squash is tender and caramelized at the edges. The flesh should be easily pierced with a fork.
While the squash roasts, combine the finely chopped scallions, juice and zest of lime, honey or agave syrup, and sesame oil in a small bowl. Stir well to blend flavors.
Once roasted, remove the squash from the oven and let cool slightly. Drizzle the scallion-lime mixture over the warm squash and sprinkle with chopped cilantro if desired. Serve immediately.