In a medium pot, combine 1 cup of vegetable broth and ½ cup of red lentils. Bring to a simmer, cover and cook for 10-15 minutes until tender.

While lentils are cooking, dice the yellow onion and red pepper. Mince the garlic and chop the cauliflower into small florets.

In a bowl, whisk together tomato sauce, brown sugar, tomato paste, Worcestershire sauce, red wine vinegar, chili powder, cumin, salt and black pepper.

Heat olive oil in a large pan over medium-high heat. Add onion, garlic, and red pepper, sauté for 2-3 minutes. Add chopped cauliflower and cook for another 2 minutes.

Pour the sauce into the pan, add the lentils, and stir everything together. Let simmer for 5 minutes until thickened.

Scoop the filling onto toasted buns and serve hot.