Rinse the lentils in cold water until the water runs clear.
Heat a large pan over medium-high heat and add the oil. Once the oil is shimmering, add onion, garlic, ginger and cook for 2 minutes, stirring frequently to prevent garlic from burning.
Add the spices and salt, and cook for 30 to 60 seconds until fragrant, tossing frequently to prevent burning.
Add the crushed tomatoes and stir for few minutes.
Pour in the water, coconut milk and finally the red lentil. Reduce the heat to low and cover the pan with a lid. Simmer for 20 to 25 minutes, or until the lentils are cooked through and have mostly softened.
Remove the lid and add the peanut butter, along with salt and pepper to taste. Continue cooking on low heat, uncovered for 5 to 8 minutes, until the curry has thickened and is creamy.
Finally, stir in the lemon juice, and turn off the heat.
