Add olive oil to a medium saucepan on medium high heat.Add the onion and cook until translucent, about 7 minutes. Add mustard seeds, ground turmeric, ground cumin, and red pepper flakes, and cook until fragrant, 1-2 minutes. Add the red lentils and stir until they're fully coated in the spiced oil mixture. Add water and coconut milk, and bring to a boil. Simmer for 25-30 minutes, until the lentils have broken apart and have formed a mash. Remove from heat. Add chopped cilantro, lemon juice, and salt. Serve over rice or cauliflower rice. Enjoy!