Heat your oven to 200C/Fan 180C/Gas 6. Halve the squash lengthways and scoop out the seeds. Slice it into wedges around 2cm thick. Line a baking tray with baking paper, lay the squash halves on the tray. Roast for 40 mins till tender and a little charred.
While the squash roasts, peel and finely chop 1 of the onions. Warm a pan over a medium heat. Add the onion with 2 tbsp water and a pinch of salt and pepper. Gently cook for 5 mins, stirring occasionally, till the onion starts to soften.
While the onion cooks, finely chop the tomatoes. Peel and crush or grate the garlic. Drain and rinse the lentils. Peel and finely slice the remaining onions.
Stir the garlic and tomatoes into the pan. Add 1 tsp each of the paprika, cumin and cinnamon. Cook and stir for 2 mins. Stir in the lentils with a pinch of salt and pepper. Simmer for 10 mins, the take off the heat. Taste and add salt and pepper if you think it needs it. Cover to keep warm.
Warm 2 tsp olive oil in a frying pan. Add the sliced onions with a pinch of salt and pepper. Cook and stir for 10 mins over a medium heat till golden. Lift out of the pan and drain on kitchen paper.
Arrange the squash wedges on 2 warm plates. Top with the lentils. Spoon over the yogurt and garnish with the mint leaves, slicing any really large leaves. Sprinkle with the rest of the smoked paprika to serve.