Place an open preserving jar onto a perforated baking tray upside down. Cut a small cross in the base to the tomatoes and place the tomatoes on the tray also. Place the tray into a pre-heated oven steam setting 100 °C for 5 minutes.
While the tomatoes steam peel and finely slice the onion and place it on a solid baking tray with picked leaves of rosemary and thyme.
Peel and finely chop the garlic and add it to the onions. Slice the “cheeks” away from the capsicum and remove any white inner pith, discard the pith and slice the capsicum into long thin strips and add to the tray with the onions.
Once the tomatoes have steamed remove the tray from the oven and set the jar aside. Peel the skin from the tomatoes and discard the skin. Roughly chop the tomatoes and add them to the other vegetables.
Season the tray of vegetables with salt, butter chilli flakes and a generous splash of extra virgin olive oil. Toss all the ingredients together by hand and scatter over small knobs of butter.
Place the tray into a pre-heated oven combi setting 150 °C for 60 minutes.
Once cooked check the seasoning and adjust if necessary, pour the contents of the tray into the preserving jar and let cool to room temperature before sealing the jar and placing it in the fridge.
Keep in the fridge for up to two weeks.