In a cooking pot or pan, heat olive oil over medium heat and cook onions for 5 minutes, until softened.
Add garlic, ginger and chili flakes. Fry for couple of minutes.
Crush coriander, mustard ad cumin seeds. Add to the pan together with garam masala and turmeric. Let cook for a minute.
Add coconut milk, vegetable stock (or water and vegetable bouillon cube), canned diced tomatoes and rinsed lentils, salt and pepper. Let cook for 15-20 minutes with covered lid until lentils are soft.
Add spinach and lemon juice, cook for another couple of minutes. Take off the heat.
Serve with rice and fresh parsley on top (or any other garnish of your choice).