Heat your oven to 220°C/Fan 200°C/Gas 7. Trim a little off the base of the squash to keep it stable on the chopping board. Cut it in half and scoop out and discard the central flesh and seeds with a large tablespoon. Cut each half into crescent moon pieces about 3cm thick, leaving the skin on.
Zest the lemon into a bowl and cut in half. Cut one half into slices.
Lay the squash in a large roasting tin and combine with the lemon slices, 2 tbsp olive oil and a pinch of salt and pepper. Place the tin into the hot oven and cook for 15-20 mins, or till tender with a little colour.
Meanwhile, finely grate the garlic into the bowl with the lemon zest and stir through 4 tbsp extra virgin olive oil and ¼ tsp salt. Drain the lentils in a sieve and rinse well under cold running water.
Prepare the chard by washing it in cold water and trimming a few mms off the stalk. If any stalks are large, cut through them lengthwise, keeping the chard in one whole piece.
Put the lentils in a medium pan and set over a moderate heat, stir through the lemon and garlic dressing and grate over a little halloumi. Place the chard on top and cover with a lid for 3 mins or till the leaves have wilted with tender stalks.
Spoon the warm lentils and wilted Swiss chard onto plates. Lay over a couple of roasted squash pieces and grate over plenty of halloumi.