01 - Combine lentils and water in a medium saucepan. Bring to a boil over high heat, then reduce heat to medium-low and simmer uncovered for 20–25 minutes until lentils are tender. Drain any excess liquid and set aside.
02 - Heat olive oil in a large skillet or pot over medium heat. Add cumin seeds and toast for 30 seconds until fragrant, being careful not to burn them.
03 - Add chopped onion to the skillet. Sauté for 4–5 minutes until soft and translucent. Stir in minced garlic and grated ginger, cooking for 1 minute until fragrant.
04 - Add diced tomato, ground turmeric, coriander, garam masala, chili powder, salt, and black pepper. Cook for 3–4 minutes, stirring frequently, until tomatoes break down and spices become aromatic.
05 - Add cooked lentils to the skillet and stir well to combine with the spice mixture. Cook for 5 minutes over medium heat, allowing flavors to meld. Add a splash of water if the mixture becomes too thick.
06 - Reduce heat to low. Gradually stir in Greek yogurt, mixing constantly to create a smooth, creamy sauce. Heat gently for 2–3 minutes, ensuring the yogurt does not curdle or separate. Adjust seasoning to taste.
07 - Stir in baby spinach and cook for 1–2 minutes until just wilted.
08 - Transfer curry to serving bowls. Garnish generously with chopped fresh cilantro and serve with lemon wedges on the side.