Heat the oven to 425. Lightly coat the squash flesh with oil, then place cut side down on a parchment lined rimmed metal baking sheet. Pierce the skin with a knife several times to allow steam to vent, then roast for 35 minutes or until the squash is firm-tender. Gently fluff some of the squash "spaghetti" strands with a fork and season with salt.
While the squash is cooking, heat a medium-large nonstick skillet over medium heat. Add the oil, then the zucchini. Cook for 3 minutes or until just tender, stirring occasionally.
Add the bell pepper, chili, and cumin, then reduce the heat to medium-low and cook for another minute, slowly stirring.
Add the corn, black beans, lime juice, and hot sauce, stirring and cooking until heated through, about one minute.
Stir in the seeds and season with salt.
Fill the cooked squash boat with the bean mixture. If using cheese sprinkle the cheese on top then place the squash back in the oven to melt the cheese, about 5 minutes.
Top with sliced cherry tomatoes, avocado, and cilantro, if you wish.