Cook the quinoa in a saucepan according to the packet instructions. You can add a little vegetable stock powder to the cooking water for extra flavour, if you like. Once cooked, remove from the heat and leave to rest, covered, for 5 minutes.
Meanwhile, steam or lightly grill the asparagus until just tender. Set aside to cool slightly, then cut into bite-sized pieces.
Drain and rinse the cannellini beans. Halve the cherry tomatoes and chop the spring onions.
If using corn on the cob, cut the kernels from the cooked or grilled cob.
Transfer the cooked quinoa to a large mixing bowl. Add the tomatoes, asparagus, spring onions, sweetcorn, cannellini beans and pumpkin seeds. Toss gently to combine.
To make the dressing, mix the lemon juice and zest with the olive oil and minced garlic, if using.
Pour the dressing over the salad and toss gently. Season with salt and freshly ground black pepper to taste, then serve.