Prepare the veg: Peel and finely slice the red onions into thin slices. Cut the top off the garlic head so that its insides are exposed, and slice the pepper into long thin strips. Finely dice the fresh parsley.
Preheat the oven: Set the oven to 200°C (392°F).
Roast the vegetables: On a large baking tray, add the sliced red onions, whole head of garlic, sliced red pepper, and cherry tomatoes. Drizzle over the olive oil, balsamic vinegar, and maple syrup. Sprinkle with a large pinch of salt and toss to coat. Roast in the oven for 20–25 minutes until the vegetables are caramelised and tender.
Prepare the garlic: Remove the baking tray from the oven. Carefully squeeze the roasted garlic cloves out of their skins and discard the husk. Mash the softened garlic with a fork and stir it into the roasted vegetables.
Add the pasta and liquids: To the same tray, add the dried pasta, vegetable stock, plant milk, chopped tomatoes, and sundried tomato pesto. Stir everything together well to ensure the pasta is evenly coated in the liquid. Cover with tin foil or aluminium foil.
Bake the pasta: Return the tray to the oven and bake for a further 25 minutes, stirring once halfway through. Bake until the pasta is soft and tender, and the sauce has thickened.
Final touches: Remove from the oven and stir in the chopped fresh parsley. Taste and adjust seasoning if needed. Sprinkle with a pinch of chilli flakes if desired.
Serve: Spoon onto plates and enjoy warm, optionally with crusty bread to soak up the delicious sauce.