Preheat the oven to 375°F
Wash the squash well, then cut off the stems. Slice the squash in half lengthwise and scoop out the seeds/guts (compost).
Place the squash cut side down on a baking sheet with a silicone baking mat (or lined with parchment paper) and bake for 30 minutes until the shell is easily pierced with a fork
While the squash is cooking prepare the filling. Heat olive oil in a large skillet over medium high heat until it shimmers.
Slice the peppers and onions and add them to the skillet. Cook about 5 minutes so that the onions are starting to get translucent and the peppers are softening.
Add the diced tomatoes, black beans, and corn to the skillet and mix with a large spoon. If your vegetables released a lot a water while cooking, you may need to drain some of it out. You want a small amount of liquid so it isn't dry, but not so much that it is submerging the vegetables.
Sprinkle the taco/fajita seasoning over the vegetable mix and toss to coat. Remove the vegetable mix from the heat, and set aside.
Shred the cheddar cheese.
When the squash is done cooking, leave them on the baking sheet, flip them over, and use a fork to scrape the flesh so that it starts forming "noodles".
Top each squash with a large spoonful of the vegetable mixture, than add a handful of cheese.
Place the squash back into the oven and bake 1-2 minutes more until the cheese is bubbly.
Set each squash half on a plate and serve with your choice of toppings like sour cream, guacamole, chopped cilantro, or green onions.
When everyone has finished eating, compost the squash "bowls"