Preheat oven to 425°. On a large rimmed baking sheet, toss the squash with 2 Tbsp. oil, and season with salt and pepper. Arrange with flesh sides down, and roast until golden and very tender, about 35 min. Flip so the other flesh sides face down, and cook 15 min. more.
Meanwhile, in a small pot, combine the orange juice and zest, tamarind, tamari, garlic, star anise, and habanero. Bring to a boil over medium heat, and cook until a thick glaze forms, about 7 min. Brush or spoon the glaze over the squash.
In a small bowl, toss the cucumber, mint, and onion with the remaining 1 Tbsp. oil, and spread over the squash. Sprinkle with flaky sea salt.
Recipe by Laura Rege.