Cube squash and halve garlic bulb. Add cherry tomatoes and toss with 2 tbsp oil, salt and pepper. Roast at 200°C for 40 minutes until soft.
Squeeze garlic from skins and set aside. Reserve ⅓ of the roasted tomatoes. Blend the remaining tomatoes with squash, silken tofu and nutritional yeast until smooth.
Boil spaghetti according to package directions and reserve some pasta water.
Warm 2 tbsp oil in a pan and stir in harissa. Add the blended mixture and lemon juice. Season with salt, pepper and a pinch of sugar.
Loosen the sauce with reserved pasta water and toss through the cooked spaghetti. Top with reserved tomatoes, basil, toasted seeds, nutritional yeast and black pepper.
