Gather all ingredients.
Wash lentils in cold water until water runs clear.
Put lentils in a pot with enough water to cover; bring to a boil and reduce heat to medium-low. Cover and simmer, adding water as needed to keep lentils covered, until tender, 15 to 20 minutes. Drain.
Heat vegetable oil in a large skillet over medium heat; cook and stir onions in hot oil until caramelized, about 20 minutes.
Mix together curry paste, curry powder, turmeric, cumin, chili powder, salt, sugar, garlic, and ginger in a large bowl; stir into onions.
Increase heat to high and cook, stirring constantly, until fragrant, 1 to 2 minutes.
Stir in tomato puree and lentils; cook until warmed through.
Serve and enjoy!