Rinse the red lentils under cold running water until the water runs clear.

In a large pot, combine the rinsed lentils and 3 cups water. Bring to a boil over high heat, then reduce to a simmer and cook for 15-20 minutes until the lentils are soft but not mushy.

Meanwhile, heat 2 tablespoons of cooking oil in a pan over medium heat.

Add 1 medium finely chopped onion to the hot oil and sauté for 5-7 minutes until golden brown.

Stir in 2 cloves minced garlic and 1 teaspoon grated ginger and cook for 1-2 minutes until fragrant.

Add 1 teaspoon turmeric powder, 1 teaspoon cumin seeds, and 1 teaspoon coriander powder, and cook for 1 minute until the spices release their aroma.

Pour the tempering into the cooked lentils and stir to combine. Simmer for 5 minutes to meld the flavors.

Season with salt to taste, stir in 1 tablespoon lemon juice if using, and garnish with fresh cilantro. Serve hot.