Peel and finely chop the onion. Warm a mediumsized pan over a medium heat for 1 min, then add 2 tsp oil and the onion. Season with salt and pepper and cook, stirring now and then, for 8 mins till the onion has softened.
While the onion fries, halve the pepper and scoop out the seeds and white pith. Finely chop the pepper. Trim and peel the carrot, then finely dice it. Trim the dry ends off the celery stick and finely chop it. Add the pepper, carrot and celery to the onion and cook, stirring once or twice, for 8 mins till all the veg have softened.
While the veg fry, peel and grate or crush the garlic. Finely chop the parsley stalks (keep the leaves for later). Tip the quinoa into a sieve and rinse under cold water for 1–2 mins (this washes off the soapy coating).
Stir the garlic and parsley stalks into the veg. Add 1 tsp each dried oregano and cumin. Add a pinch of cayenne pepper – it's spicy so use as much or as little as you prefer. You can always add more later. Stir to mix well.
Drain the beans and stir them in with the quinoa. Tip in the tin of chopped tomatoes. Pour in 200ml boiling water. Pop on a lid and bring to the boil, then reduce the heat and simmer for 12-15 mins. Stir every so often till the chilli thickens and the quinoa cooks and becomes tender.
Roughly chop the parsley leaves. Have a taste and add a pinch more salt, pepper or cayenne if it needs it. Spoon into warm.