Preheat oven to 180°C. Spray 2 oven trays with cooking oil spray. Arrange eggplant slices in a single layer on oven trays; drizzle with the olive oil and sprinkle with salt. Toss to evenly coat with your hands. Roast for 20 minutes, turning after 10 minutes, or until tender and golden. Set aside to cool.

Heat oil in a saucepan over medium heat. Add onion and cook for 5 minutes or until light golden. Add the sausages and fry until browned and cooked through. Stir garlic through and cook until fragrant. Add the tomatoes and bring to a simmer. Reduce heat to low and simmer for 10 minutes or until sauce thickens. Season with salt to taste, a pinch of sugar, stock powder and basil.

Place ricotta, pesto, salt and pepper in a bowl and mix until well combined.

Grease a 6cm deep, 20cm (base) square ovenproof dish. Spread a third of the tomato sauce over the base of the pan. Add the eggplant slices over the top. Sprinkle 1/3 of the cheese over the eggplant. Layer with another layer of sauce, eggplant and mozzarella cheese. Repeat layering with eggplant, sauce and half of the ricotta. Finish the top layer with sauce and remaining ricotta. Sprinkle with cheese. Bake for 20 minutes or until the cheese is golden and bubbling. Serve.