Heat olive oil in a large pot over medium heat and sauté the diced onion for 5 minutes until softened.
Add minced garlic, cumin, cayenne pepper, and smoked paprika, stirring for 1 minute until fragrant.
Add the rinsed red lentils, crushed tomatoes, and vegetable broth, then bring to a boil.
Reduce heat to low and simmer for 25 minutes, stirring occasionally, until lentils are completely tender and broken down.
Season with salt and pepper, stir in lemon juice, and use an immersion blender to partially blend for a creamier texture if desired.
Serve hot, garnished with fresh herbs or a dollop of Greek yogurt if calories allow.