Create the sauce by chopping the onion, mincing the garlic and adding it to a large, shallow casserole dish with the dried herbs, vinegar, passata and red pesto. Give it all a good stir then cover with a lid and leave to one side while you cut the vegetables.
Wash the audergine, tomatoes and courgette and peel the sweet potatoes. Slice each roughly 5mm thick.
When you have sliced enough to fill the casserole dish, start placing them from the outside, in a circular shape around the edge. Continue until you reach the middle.
Place it in the oven covered with a lid or foil and bake in a preheated oven at 180 degrees C for 30 mins.
After 30 mins, remove the lid/foil and bake for a further 30-40mins.
When it's ready, it will have reduced and the edges of the veggies will have become crispy.
Use store bought or home made pesto and drizzle it over the top of the ratatouille with a spinkle of dried herbs before serving.