Heat the olive oil in a large pan over medium heat. Add the onion and sauté for 5 minutes until translucent. Add the garlic and red bell pepper and sauté for 5 minutes, until tender.
Move the vegetables away from the center and add the ginger, cumin, garam masala, ground coriander, and cayenne pepper, plus optional spices and sauté for 1-2 minutes, until the spices are toasted.
Add the diced tomatoes, coconut milk, precooked green lentils, and chickpeas, and bring to a boil.
Reduce the heat, cover, and simmer for 20 to 25 minutes until the lentils are tender.
Add the spinach and cook for another 2 to 3 minutes, until wilted. Add 1 teaspoon of salt.
Remove from the heat and add the lemon juice. Salt and pepper to taste.
Serve hot, accompanied by basmati rice or naan.
Stored in an airtight container, this chickpea and lentil curry will keep for up to 3 to 4 days. To keep it longer, freeze it in a suitable freezer bag or container for about 2 to 3 months.