Heat olive oil over medium heat in a large pot. Add sliced onions and salt, stirring occasionally for about 15-20 minutes until golden brown and sweetly fragrant.

Stir in minced garlic, ground cumin, and smoked paprika. Cook for another 1-2 minutes until fragrant.

Toss in diced carrots and cook for 5 minutes until slightly softened.

Add rinsed red lentils, vegetable broth, and canned diced tomatoes. Stir and bring to a boil.

Reduce heat to low, cover, and let simmer for about 20 minutes until lentils are tender.

If desired, use an immersion blender to puree the soup for a smooth consistency.

Stir in lemon juice, salt, and pepper to taste. Adjust seasoning and garnish with fresh herbs before serving.