Prep: Preheat oven to 400°F (204°C). Cut spaghetti squash in half lengthwise and scoop out the seeds. Drizzle the inside with 2 Tbsp of olive oil, then sprinkle with chili powder, cumin, and salt. Rub to evenly coat. Place cut-side down on a baking sheet and prick the outside with a fork.
Roast: Roast for about 30 minutes, or until fork tender but still a little firm. When finished, flip over and allow to cool enough to touch. Leave the oven on.
Sauté: While squash cooks, heat the remaining 1 Tbsp of oil in a large sauté pan over medium heat. Add pepper and onion, stirring and cooking until soft, about 15 minutes.
Sauce: While squash cooks, also make your sauce by stirring together all sauce ingredients.
Spaghettify: Use a fork to scrape strands from the inside of the spaghetti squash. Transfer strands to a separate bowl, leaving about ¼ inch of flesh in the squash to support your bowls.
Assemble: Into the hollowed out squash bowls layer in sautéed pepper/onions, corn, beans, sauce, spaghetti squash strands, and cheese. Return to the oven for 5 to 10 minutes, or until cheese is melted.
Store leftovers in an airtight container in the fridge for 3 to 4 days.