Method

• 1.
  Heat the olive oil in an ovenproof frying pan over medium heat. Add the onion and cook, stirring frequently, for 10 minutes or until starting to brown. Add the garlic and cook for 2 minutes or until fragrant, then add the tomatoes and oregano and cook, stirring well, for 5 minutes. Add the brown sugar, vinegar and some salt and pepper, and stir well to combine.
• 2.
  Add a splash of water, then reduce the heat to a gentle simmer and cook for 10-15 minutes, until very thick and rich. Meanwhile, preheat the oven to 200°C fan-forced.
• 3.
  Toss the zucchini and mozzarella in a generous drizzle of olive oil and season. Take the pan off the heat, check the seasoning and adjust if necessary. Starting at the outer edge, arrange the zucchini in concentric circles, overlapping each slice by about a third and placing at an angle so they nestle in the sauce. Add a slice of mozzarella for every 3-4 slices of zucchini.
• 4.
  Transfer to the oven and bake for 20-30 minutes, until the top is brown and sauce is bubbling up through the zucchini.
• 5.
  Meanwhile, combine all the ingredients for the gremolata in a mortar with some salt and pepper and, using the pestle, pound for 1-2 minutes to create a chunky paste. If you don’t have a mortar and pestle, simply add the ingredients, except the juice and oil, to a large chopping board and chop until well combined. Add to a bowl, stir through the juice and oil and season. Taste the gremolata and adjust the seasoning if necessary. Add an extra drizzle of olive oil, or 1 tbs of water, to loosen the gremolata to a spoonable consistency.
• 6.
  Serve the ratatouille fresh from the oven, dotted with the gremolata and an extra drizzle of olive oil.