Preheat the oven to 200 C (400 F/gas 6). Line a baking tray with baking paper.
Cut the squash or pumpkin in half. Scoop out the middle and piece the back of each half three or four times with a knife.
Place both halves of the squash, cut side down, on the prepared tray. Bake for 30-40 minutes (depending on the size of the squash) until the outside gives a little when you press on it. Remove from the oven and set aside.
Meanwhile, combine the onion, garlic, pepper and cauliflower in a saucepan over a medium heat and saute in 1-2 tablespoons of water for 2-3 minutes, adding more water as necessary to prevent burning.
Add the spices and continue to cook until the onion is translucent (approximately 5 minutes).
Add the corn, beans and quinoa and continue to cook, stirring and adding the water as necessary to prevent burning, for another 5 minutes.
Divide the onion mixture in half (you are likely to have leftover filing), flip the squash halves over and add the filling in each scooped out portion. Top each half with 3 teaspoons of salsa and return to the oven to bake for 10 minutes.
Remove from the oven and top with the avocado slices and the remaining salsa and serve.
