Rinse the lentils thoroughly under cold water until the water runs clear, then set aside.
Heat a skillet over medium heat and toast the cumin seeds until fragrant, about 30 seconds. Remove from heat and set aside.
Add a splash of oil to the skillet, then sauté the chopped onion and diced carrots until they soften and turn slightly golden, about 5 minutes. The kitchen fills with a sweet, aromatic smell.
Add the minced garlic to the skillet and cook for another minute until fragrant, stirring constantly so it does not burn.
Transfer the sautéed vegetables and toasted cumin to your slow cooker. Pour in the vegetable broth and stir to combine everything evenly.
Stir in the rinsed lentils, making sure they are submerged in the broth. Cover with the lid and set the slow cooker on low for 6-8 hours or high for 3-4 hours.
Halfway through cooking, check the soup and give it a gentle stir. Season with salt and pepper to taste, and add a squeeze of lemon juice for brightness.
Once the lentils are tender and the soup has thickened to a velvety consistency, turn off the slow cooker and let it sit uncovered for 10 minutes to settle the flavors.
Scoop the soup into bowls, garnish with fresh herbs if desired, and enjoy a warm, hearty bowl that’s full of flavor and comforting texture.
