Rinse the lentils thoroughly under cold water and set aside. Dice the onion finely and mince the garlic. Gather all ingredients nearby.
Heat the large skillet over medium heat and add a splash of oil. Once shimmering, add the diced onion and sauté for about 5 minutes until translucent and fragrant, the edges turning a light golden.
Add the minced garlic to the skillet and cook for another 30 seconds until you smell a fragrant aroma, stirring constantly to prevent burning.
Pour in 2 cups of water and stir in the rinsed lentils. Bring the mixture to a boil, then reduce the heat to low. Cover the skillet loosely and simmer gently for 25-30 minutes, stirring occasionally, until the lentils are tender but still hold their shape.
While the lentils cook, in a small bowl, mix the tomato sauce, Worcestershire or soy sauce, smoked paprika, and cumin. Set this flavorful mixture aside.
Once the lentils are tender and most of the water has been absorbed, stir in the sauce mixture. Increase the heat slightly and cook uncovered for another 10 minutes, allowing the sauce to thicken and the flavors to meld, filling your kitchen with smoky, tangy aromas.
Taste the filling and adjust seasoning if needed. Remove from heat and let sit for 3-5 minutes to allow flavors to settle and the mixture to thicken further.
While the filling rests, lightly toast the buns in the skillet, cut sides down, for about 1-2 minutes until golden and slightly crisp.
Use a slotted spoon or ladle to generously scoop the smoky lentil filling onto the toasted buns, piling high for a messy, satisfying look.
Add optional toppings like pickles, shredded lettuce, or cheese to add contrast and freshness. Serve immediately while hot and enjoy the hearty, plant-based comfort of these sloppy Joes.
