Rinse lentils in a fine-mesh sieve under cold water until running clear, removing any debris. Drain thoroughly.

Heat olive oil in a skillet over medium heat. Add chopped onion and minced garlic. Sauté until soft and translucent, about 5 minutes.

Stir in smoked paprika, ground cumin, and salt to taste. Cook for about 1 minute to bloom the spices.

Pour in tomato sauce and vegetable broth, stirring to coat. Add drained lentils and mix to combine.

Bring to a gentle bubble, reduce heat to low, cover, and simmer for 20–25 minutes, stirring occasionally.

Stir in Dijon mustard and maple syrup. Cook 2 minutes more to meld flavors.

Toast burger buns until golden brown, about 2–3 minutes.

Spoon a generous portion of the lentil mixture onto each bun. Top with pickles and leafy greens if desired. Serve immediately.