Makes about 3 litres of sauce

• 115g butter
• 110g minced onion
• 75g minced garlic
• 
Zest of 2 lemons
• 5 tablespoons freshly squeezed lemon juice
• 1 ltr ketchup
• 
240ml passata
• 
150g light brown sugar
• 6 tablespoons molasses
• 125ml Worcestershire sauce
• 
65g chili powder
• 4 tablespoons white wine vinegar
• 1 ½ tablespoons chipotle puree
• Pinch of  salt
• 750ml water

Melt the butter in a large heavy-bottomed pot over medium heat. Add the minced onions and cook for 5 minutes. Add the garlic and cook for another 5 minutes. Stir in the lemon zest, lemon juice, ketchup, passata, brown sugar, molasses, Worcestershire sauce, chilli powder, vinegar, chipotle puree, salt and water and bring to a boil. Lower the heat and simmer for 30 minutes, stirring frequently.