1 Preheat oven to 180°C. Line a large baking tray with baking paper. Arrange the sweet potato slices in a single layer on the tray. Spray with olive oil and cook for 30 minutes, turning over and spraying slices again halfway through cooking time.
2 Wash, dry and shred spinach and kale, keeping separate. Place oil, shallots and garlic in a large, deep non-stick frying pan. Heat over medium heat until the mixture starts to sizzle, then add spinach. Toss until wilted. Transfer to a large bowl. Add kale to pan and toss until wilted; add to the spinach. Cool, tossing from time to time to release heat. Add the lemon zest, and season mixture with cracked black pepper.
3 Melt the olive oil spread in a small saucepan over medium heat. Add the flour and cook, stirring, for 1 minute. Add milk a little at a time, stirring until smooth between each addition. Bring to a simmer and cook for 1 minute. Remove from heat and stir in 1 cup of cheese.
4 Lightly spray a 24cm round ovenproof dish with olive oil, then spread ½ cup of passata over the base. Use scissors to cut lasagne sheets to cover base. Spread half the spinach mixture over the pasta. Reserve ½ cup cheese sauce for the top, and drizzle half of the remaining sauce over the spinach.
5 Top with another layer of lasagne, cutting to fit. Top with remaining spinach mixture, sweet potato and remaining passata. Arrange remaining lasagne sheets on top, cutting to fit. Arrange zucchini slices on top in a lattice pattern.
6 Use the back of a spoon to spread the reserved cheese sauce over, then sprinkle with remaining cheese. Cover with foil and bake for 20 minutes. Remove foil and cook lasagne a further 10 minutes.
7 Meanwhile, make basil pesto: Combine all ingredients in a food processor and blitz until combined. Serve lasagne with pesto, sprinkled with pine nuts and microherbs, if using.