Heat the olive oil in a large pot over medium heat. Add the onion and garlic and cook until the onion softens.
Add the potatoes and cook for 3 minutes, stirring now and then.
Stir in the lentils, smoked paprika, cumin, and bay leaf until everything is coated with the spices.
Pour in the vegetable broth and diced tomatoes. Add salt and pepper to taste.
Bring the mixture to a boil, then lower the heat and simmer for 30 to 35 minutes until the lentils and potatoes are tender.
Remove the bay leaf before serving. Spoon the stew into bowls and top with chopped parsley.