Heat a soup pot over high heat. Add the Extra-Virgin Olive Oil (3 tablespoon) and then the Yellow Onion (1) and seaon with Salt (1 teaspoon). Stir, turn the heat to low, and cover the pot.
Check and stir after a few minutes, letting the moisture on the lid drip back into the pot to keep things steamy. Lower the heat if there is any browning going on, and re-cover. Cook like this until the onion is tender, about 15 minutes.
Add the Cumin Seeds (1 tablespoon), Whole Coriander Seeds (1 tablespoon), Fennel Seeds (1 teaspoon), and Crushed Red Pepper Flakes (1/2 teaspoon) and cook, stirring for 1 minute to toast the spices.
Add the Ground Turmeric (1 tablespoon) and stir for 30 seconds more. Add the French Green Lentils (1 cup), Brown Lentils (1/2 cup) and Water (4 cup) and bring to a boil.
Lower the heat to a simmer and cook, stirring occasionally, until the lentils give up their earthly bodies and become one with your dinner, about 30 minutes.
Taste, and adjust seasoning as necessary. Serve with Fresh Cilantro (to taste), Yogurt (to taste) and Flatbread (to taste) if desired.