Rinse the red lentils thoroughly under cold water until the water runs clear.
Dice the yellow onion, mince the garlic, and grate or finely chop the ginger.
In a medium saucepan, heat the olive oil over medium heat. Sauté the diced onion, garlic, and ginger until translucent and aromatic.
Add the turmeric, cumin, and coriander powders to the pan. Stir for about 30 seconds to toast the spices and release their flavors.
Add the rinsed red lentils, diced tomatoes, and light coconut milk to the saucepan. Stir well to combine all the spices and ingredients.
Pour in about 1 cup of water, bring the mixture to a simmer, then reduce the heat. Cover and let it cook for 20-25 minutes, stirring occasionally, until the lentils are tender and the curry has thickened.
In the last few minutes of cooking, gently fold in the fresh spinach and allow it to wilt into the curry.
Taste and adjust seasonings as needed, then serve warm.