In a large dutch oven set over medium high heat, heat olive oil and add the onion, carrots, and potatoes. Saute for 3 minutes or until softened.
Add the garlic and cook for 30 seconds.
Add the lentils, cumin, salt, pepper, stock cube, and water.
Give everything a stir, bring to a boil then reduce to a simmer. Cover partially with a lid, and cook for 30 minutes or until the lentils have softened. Remove from heat.
Right before serving stir in fresh lemon juice (start with 1 tablespoon). Taste and adjust the lemon, salt, and pepper as needed.
Serve with fresh chopped parsley, and warmed pita bread.