Rinse the red lentils thoroughly under cold water and set aside.
Heat a non-stick pot over medium heat. Add a splash of water or a small amount of cooking spray if needed, then sauté the chopped onion, minced garlic, and grated ginger until the onion becomes translucent.
Stir in the curry powder, ground cumin, and turmeric, cooking the spices for about 30 seconds until fragrant.
Add the red lentils, diced tomatoes, and water to the pot. Bring to a gentle simmer and let cook for 15-20 minutes, stirring occasionally until the lentils are soft and have begun to break down.
While the lentils are cooking, press the firm tofu to remove excess moisture. Cube the tofu into bite-size pieces.
When the lentils are almost done, stir in the cubed tofu and light coconut milk. Allow the curry to simmer for an additional 5 minutes to meld the flavors.
Fold in the baby spinach and cook just until wilted. Adjust seasonings as needed.
Serve the curry warm, enjoying its creamy, spicy, and satisfying flavor.