Wash squash, peel, remove seeds and cut into 2-inches pieces.
Heat vegetable oil in a pot over medium heat, add diced onions and fry until slightly golden, stirring occasionally. Save 2 tablespoons of golden onoions for garnish.
Add lentils, water, salt and pepper to the remaining golden onoins. Cover the pot, heat over medium-low and simmer until lentils are tender, stirring occasionally. Then add squash; cover and simmer until those are tender. Add more water during cooking if necessary.
Add lemon juice, stir well and simmer until almost all the liquid is absorbed.
Garnish with golden onions before serving.