Heat olive oil in a large pot over medium heat.

Add chopped onions, mushrooms, zucchini, and minced garlic to the pot.

Cook and stir the vegetables over medium heat for about 5 minutes.

Add dry lentils and 3 cups of water to the vegetables.

Increase heat to bring the mixture to a boil, stirring occasionally.

Reduce heat to low, cover the pot, and cook for 45 to 60 minutes.

Stir in tomato sauce, tomato paste, sugar, and 1/2 cup of water.

Bring the sauce back to a boil.

Reduce heat, cover the pot, and simmer for 20 minutes.

If necessary, add more water to prevent sticking.

Ensure the sauce remains thick, avoiding excessive dilution.