Step 1

Heat oil in a large saucepan over medium heat. Add onions and cook, stirring, for 5 minutes or until soft. Add garlic and cook for 1 minute.

Step 2

Add tomatoes, cover and bring to the boil over high heat. Reduce heat to medium-low. Cook, covered, for 5 minutes. Add sugar and season with salt and pepper. Transfer 500ml (2 cups) to a bowl. Cover and place in fridge.

Step 3

Add lentils and stock to pan. Bring to the boil over high heat. Reduce heat to low. Cook, covered, stirring often, for 15 minutes or until tender.

Step 4

Add zucchini and cook, stirring, for 5 minutes or until zucchini is soft. Transfer mixture to a heatproof bowl, season with salt and pepper, and set aside for 10 minutes. Cover and place in fridge for 30 minutes or until cold.

Step 5

Preheat oven to 200°C. Spread 1/2 cup of tomato sauce over base of a 21 x 33cm (base measurement), 6cm-deep (3-litre/12-cup) ovenproof dish. Place 1 lasagne sheet on top. Cut a strip from another sheet to fill gaps. Spread half of lentil mixture evenly over lasagne and place another lasagne sheet on top. Crumble over ricotta and use wetted fingertips to spread. Cover with another lasagne sheet, remaining lentil mixture and final lasagne sheet. Spread over remaining tomato sauce and sprinkle with cheddar.

Step 6

Bake in preheated oven for 40-45 minutes or until tender and golden.