Heat the olive oil in a large deep saucepan and add the red onion and saute over a low heat for 8-10 minutes until softened but not coloured. Stir in the garlic, sage and pork mince and cook for 5 minutes stirring occasionally until lightly browned. Add the spinach, lemon rind and juice and cook until the spinach has wilted. Increase the heat and cook to drive off any excess liquid. Season with salt and freshly ground black pepper. Allow to cool slightly.
Pre-heat then oven to 200*C, 180*C fan oven, Gas Mark 6. Pour the tomato pasta sauce into a large ovenproof dish. Lay the lasagne sheets out on a work surface and spread with the ricotta cheese. Divide the minced pork mixture between the lasagne sheets spooning it along one short end of each sheet. Roll up and arrange seam side downwards on top of the pasta sauce.
Heat the milk and butter in a pan until the butter has melted. Whisk in the flour and beat until smooth and thick. Cook for 1 minute stirring occasionally. Stir in the cheddar cheese and cook until melted. Season to taste and pour over the cannelloni rolls. Bake for 25 minutes. Scatter over the cherry tomatoes and Parmesan cheese and bake for a further 10 minutes until bubbling and golden.
Freezing and defrosting guidelines
Once the dish has cooled completely, transfer it to an airtight, freezer-safe container, seal and freeze for up to 1-3 months. To serve, defrost thoroughly in the fridge overnight before reheating. Loosely cover with foil and bake until dish is thoroughly heated through. Reheat until piping hot.
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