Lovely antique idea before industrial age started. Simply putting tomatoes, a peeled halved onion, butter and salt in a pot and cooking them with barely an occasional stir until they are reduced produces a deliciously concentrated sauce.

Bring butter, sugar, tomatoesvand onion to a boil in a 4-qt saucepan over medium-high heat. Reduce heat to medium-low and cook, stirring occasionally, until flavours meld and sauce is slightly reduced, about 45 min.

Discard onion and season sauce with salt and pepper before serving.