- Place large sauté pan over medium heat. Add olive oil and vegetables, sauté 3-5 minutes. Onions will become see-through and bell pepper will be tender but firm.
- Remove pan from heat. Add the mustard powder and paprika to the pan. Stir to mix well. Let the heat from the pan toast the spices and become fragrant.
- Add brown sugar, Worcestershire, tomato sauce and apple cider vinegar. Return to heat and stir well. Bring to gentle simmer. Cover and cook for 10 minutes.
- Add lentils to sauce, stirring to combine well. Cover with lid and simmer an additional 5 minutes.
- Taste – add salt if desired.
- Sprinkle flour over lentil mixture a little bit at a time to avoid clumping, stirring as you add. Mix well and gently simmer uncovered until the mixture is as thick as you want it. More flour can be added (if necessary) for a very thick mixture that stays on the bun better.
- Top each bun with lentil mixture and serve.
Other serving suggestions:
- Add pickles for a crunchy flavor boost.
- Serve with eggs for a hearty breakfast meal.
- Pair with blue corn tortilla chops for a huevos rancheros skillet.