Heat the olive oil in a large pot over medium heat. Add the diced onion and cook until it softens.
Stir in the garlic and ginger. Cook for one minute until fragrant.
Add the cumin, turmeric, and curry powder. Stir for 30 seconds to toast the spices.
Pour in the rinsed red lentils, diced tomatoes with their juice, and vegetable broth. Bring the mixture to a boil.
Reduce heat to low, cover, and simmer for 20 minutes until the lentils are soft and the soup thickens.
Stir in the fresh spinach and cook for 2 minutes until it wilts. Season with salt and pepper.
Serve hot with lemon wedges on the side.