Chop the bell pepper and onion. Mince the garlic. Set aside.
Add the lentils and water or vegetable broth to a sauce pan. Vegetable broth gives the lentils more flavor than water. Bring to a boil, cover, reduce to low, and cook 18-22 minutes until done.
While the lentils are cooking, warm 2 tablespoons olive oil in a large skillet over medium-low heat. Once warm, add in the onion, bell pepper, and garlic. Cook until the pepper is tender and the onion is almost translucent. Add in the tomato sauce, Worcestershire sauce, and spices. Adjust to taste. I prefer the smokiness of Worcestershire, so I add a lot of it. Stir to combine.
Add the cooked lentils to the red sauce and cook 4-5 minutes, stirring frequently. The sauce will sputter, so stirring limits air bubbles.
Butter and broil hamburger buns until toasted. Spoon on the sloppy joe mixture.