Cook pasta in salted water until al dente, then drain and reserve ½ cup cooking water.
Heat olive oil in a pan and sauté onion until soft and translucent.
Add garlic and cook 30 seconds until fragrant.
Stir in tomato puree, tomato paste, seasoning, chili flakes, salt, and pepper.
Simmer sauce for 10 minutes until slightly thick.
Add cooked lentils and mix gently.
Add pasta and splash of reserved water, tossing to coat evenly.
Cook two minutes until glossy and well combined.
Finish with fresh herbs and serve warm.