Water the roman pot. Wash, clean and cut vegetables into pieces.
Peel, quarter and slice the onion. Peel and chop garlic. Mix the vegetables, onion and garlic in the Roman pot, seasoning with salt, pepper and sugar in between.
Place thyme sprigs between the vegetables. Pour olive oil and broth over them. Cover and cook in oven at 230° convection for 30 minutes (be sure to put the Römertopf in a cold, not preheated oven!).
Finally, remove the thyme stems and stir in the tomato paste.