Fill a large sauce pan with water, add a teaspoon of salt and bring to a boil.
Chop all your vegetables ready. Add your squash cubes into the boiling water and boil until tender. This will take around 5-10 minutes.
Cook pasta as per packet instruction.
Meanwhile, add your oil or oil spray to a frying pan over a medium heat. Add the chopped onions and garlic and fry for around 5 minutes. Take care not to burn, as this will give an unpleasant bitter taste to your sauce. Add the chopped pepper and the chilli flakes and fry until pepper is soft.
Drain your cooked butternut squash cubes and cool them down by rinsing under a cold tap. Then add these to your blender. You may need to blend in stages depending on how big your blender or food processor is. Add the cooked onion, garlic and pepper to the blender. Add the drained tofu, mustard and salt and pepper. Blend until smooth. Add in the stock until you gain a smooth sauce consistency.
If you do not have a food processor or blender you could add the butternut squash to the frying pan with the onion, garlic and pepper and use a hand blender to blend until smooth.
Add juice of lemon at the end and adjust seasoning to your liking.
Drain pasta (keep some of the water) add sauce and mix. If you need to loosen the sauce, use a splash of the pasta sauce.