Rinse the brown lentils under cold water until the water runs clear, then set aside.
Dice the onion and carrots into small, even pieces for even cooking, and mince the garlic finely.
Heat the olive oil in a large skillet or Dutch oven over medium heat until shimmering, and add the diced onion and carrots. Sauté for about 8 minutes, stirring occasionally, until they turn soft and fragrant, filling the kitchen with a sweet aroma.
Add the minced garlic and cook for an additional 30 seconds, stirring constantly until fragrant, but be careful not to let it burn.
Stir in the tomato paste and cook for 2 minutes, allowing it to toast slightly and deepen in color, releasing a rich, umami smell.
Pour in the vegetable broth and add the rinsed lentils, stirring to combine. Bring the mixture to a gentle simmer.
Add the bay leaf, a sprig of thyme, and a pinch of chili flakes. Partially cover the skillet and simmer gently for 25 to 30 minutes, stirring occasionally, until the lentils are tender and the sauce has thickened to a velvety consistency.
Remove the bay leaf and thyme sprig, then taste the ragu and season with salt and pepper as needed. Let it rest off heat for 5 minutes to allow flavors to meld.
Finish by drizzling a little extra virgin olive oil over the top and serving hot, ideally over grains or with crusty bread for a cozy, satisfying meal.
