Rinse the lentils and soak in water for several hours or overnight. Drain before cooking.
Finely chop the onion, garlic, and bell pepper. Cut the carrots into small pieces.
Heat olive oil in a large pan over medium heat. Add the onion and garlic and cook for 4–5 minutes until softened.
Add the bell pepper, carrots, soaked lentils, water, coconut milk, and vegetable stock cube. Stir well.
Add cumin, curry powder, and turmeric. Bring to a gentle boil, then reduce heat and simmer for about 25 minutes, stirring occasionally. (If lentils were not soaked, cook 30–35 minutes.)
Taste and season with salt as needed. Serve warm with cooked rice.