To prepare an easy gluten-free quinoa bake with zucchini start cooking the quinoa according to the packet instructions. Drain, rinse and set aside.
Bring a large pan of salted water to a boil and blanch the zucchini for 2 minutes. Drain well and set aside.
Heat the oven to 200C (180C fan).
Melt the butter in a pan and stir in the flour. Cook for 2 minutes, stirring all the time then add the milk and the mustard.
Bring to a boil, then turn the heat down and cook gently for 10 minutes, stirring occasionally. Season with salt and pepper.
Layer the quinoa and zucchini in an ovenproof dish, finishing with a layer of zucchini. Pour over the sauce and bake for 30 minutes until bubbling and brown: the quinoa bake is ready to be served.