Heat oil in a large non-stick frypan over medium heat. Cook onion and red pepper for 5 minutes, add courgette and cook for a further 4-5 minutes until tender. Stir through baby spinach, season with salt and pepper and transfer to a large bowl to cool slightly.

Wipe out frypan and return over a medium heat. Place half the tortillas on a board and sprinkle with half the cheese. Top with vegetables, remaining cheese and tortillas. Transfer one of the quesadillas to the frypan and cook for 2 minutes each side until golden and cheese has melted. Repeat with remaining quesadilla. Cut into wedges and serve with yogurt.