Upside-down Gingerbread with Pears

Name: Upside-down Gingerbread with Pears
Prep time: 10 min
Cook time: 1 h
Total time: 1 h
Yield: 12 portions
Ingredients: 2 tsp lemon juice; 110 g milk; 100 g unsalted butter; 220 g brown sugar; 400 g tinned pears; 30 g walnut halves; 75 g black treacle; 1 large egg; 110 g plain flour; 2 tsp ground cinnamon; 1 tsp ground ginger; ½ tsp bicarbonate of soda; ¼ tsp fine sea salt; ¼ tsp ground nutmeg; 1 pinch ground cloves