Preheat the oven to 200°C/Fan 180°C/Gas 6. Spoon 1 tsp Cajun spice mix into a bowl. Add 2 tbsp olive oil and a pinch of salt. Halve the squash lengthways. Scoop out the seeds with a spoon. Rub the spice mix on to the cut side. Place the squash halves cut-side-down on a lined baking tray. Slide them into the hot oven and roast for 40 mins.
While the squash is roasting, prepare the spiced quinoa stuffing. Rinse the quinoa and shake dry. Peel and finely chop the onion. Finely dice the tomatoes. Peel and grate the garlic. Finely chop the chilli, flicking out the seeds.
Set a medium pan on the heat. When warm, drizzle in ½ tbsp oil. Add the onion and cook for 5 mins till softened. Add the tomatoes, garlic and chilli and cook for 1 min. Add the rinsed quinoa with ½ tsp Cajun spice mix. Pour in 150ml boiling water. Simmer on a gentle heat for 15 mins till the water has absorbed.
Slice the kernels from the corn. Add them to the quinoa after it has cooked for 15 mins and fold them through.
Finely slice the radishes. Zest and juice ½ the lemon. Toss the radishes with a little lemon juice. Halve the avocado and scoop out the flesh. Mash it till smooth with a pinch of salt and pepper and a squeeze of lemon.
Remove the squash halves from the oven. The skin should be softened and the flesh fluffy. Scoop out most of the flesh, leaving a 1cm border.
Add the flesh to the cooked quinoa and stir together. Taste and season. Spoon the filling back into the squash shells – they should be piled high.
Put handfuls of the salad mix onto two plates. Top with the radishes. Place a stuffed squash half onto each plate. Dollop on the mashed avocado. Scatter over the lemon zest and a dusting of Cajun spice.