Caramelize the onions: In a wide skillet with a little olive oil, cook the onions over medium heat until deeply golden and caramelized. For the best flavor, caramelize them slowly with occasional splashes of water for about 30 minutes (or longer).
Prepare the filling: Add the cooked lentils and the spices (mixed with a little boiling water) to the skillet. Stir for 2–3 minutes to let the flavors combine. Lightly mash some of the lentils with the back of a spoon to create a stickier texture that holds together inside the pita. If needed, add a little cornstarch.
Fill the pitas: Stuff each pita with the lentil mixture and press firmly.
Brush and grill: Heat a grill press, panini maker, or grill pan. Generously brush the pitas on all sides with the seasoned olive oil mixture, especially around the opening where the filling is exposed.
Cook: Grill until the pita is deeply golden and crispy, and the filling is hot with crispy edges.
Serve: Enjoy hot with tahini and an Israeli salad.
