Heat a large, deep skillet over medium-high heat. Add the oil. Once hot, add the garlic, ginger, turmeric, and serrano. Cook for two minutes, stirring frequently to prevent burning.

Add the ground spices and salt. Cook for 30 to 60 seconds, until fragrant, stirring frequently.

Pour in the vegetable broth and deglaze the pan. Add the lentils and crushed tomatoes and stir to combine. Reduce the heat to low. Simmer, covered, for 20 to 25 minutes, until the lentils are cooked through.

Stir in the coconut milk and tahini. Continue cooking on low heat, uncovered, for about 5 minutes more, until the curry is thick and creamy. Add the cilantro and lemon juice, stir, and serve.