Preheat the oven to 100°C and line a baking tray with baking paper.
Peel and deseed the tomatoes and cut into petal shaped pieces.
Place tomato ‘petals’ on the baking tray and drizzle with olive oil, then sprinkle with salt and sugar. Add the garlic cloves and sprigs of thyme. Roast for 1 hour.
Set the cooking liquid aside and transfer the tomato petals to a wire cooling rack.
Remove the stamens and trim the courgette stems.
Separate 6 flowers from the courgettes; slice the flowers and reserve for the filling. Thinly slice the 6 courgettes on a mandolin for the decoration.
Cut 3 pearl onions into quarters and grill on the flat side, set aside. Slice the trumpet courgette and remaining new pearl onions, then in a pan sweat over a low heat with olive oil. If needed, add water or vegetable stock and bring to a simmer, making sure the colour does not change as the liquid is reduced.
Once cooked and cooled, roughly chop the cooked vegetables. In a bowl, mix the vegetables with the shredded basil, ricotta, egg yolk, Parmesan and the 6 sliced courgette flowers.
Transfer to a disposable pastry bag and snip off the end of the bag. Pipe into each courgette flower.
Peel and deseed the tomatoes, sweat oven a high heat in olive oil. Deglaze with the wine vinegar, then add the tomato ketchup. Remove from the heat and season, then using a blender, blend until smooth.
Pan fry the courgette slices in olive oil until just soft, about 30 seconds. Cut the gem lettuce into 4 - 6 pieces.
Spoon the tomato sauce into the centre of the circle and decorate with the grilled onion quarters, softened courgette slices and chives. Pour the reserved oven-roasted tomato cooking liquid around the dish.