Step 1

Heat olive oil in a pot over medium heat. Cook red onion in hot oil until browned, 7 to 10 minutes.

Step 2

Pour lentils into the pot with onion; add enough water to cover the lentils by 2 to 3 inches. Bring the water to a boil and reduce heat to medium-low.

Step 3

Stir tomato paste, garlic, brown sugar, and paprika into the lentil mixture to integrate the paste smoothly into the liquid; bring to a simmer and cook until the lentils are tender, about 1 hour.

Step 4

Stir kale into the lentils, reduce heat to low, and cook until the kale is tender, 10 to 15 minutes; season with salt and freshly ground black pepper.