Preheat your oven to 375°F (190°C). Heat the oil in a large saucepan or deep frying pan over low heat. Add the onions and cook gently, stirring from time to time, for 3–5 minutes until they become soft and translucent. Stir in the curry paste and continue cooking for 2 minutes to release its aromatic oils and deepen the flavor.
Add the eggplant and red bell peppers to the pan and cook for 10–15 minutes, stirring occasionally, until the vegetables are completely soft and tender. Season with salt and pepper to taste, then remove from the heat and set aside to cool.
While the vegetables are cooling, place the lentils in a separate pan and cover them with water. Bring to a boil, then reduce the heat and simmer for 15 minutes or until the lentils are just tender but not mushy. Drain thoroughly and let them cool.
Once both the vegetables and lentils have cooled, combine them in a large bowl. Fold in the cubed cheese, mixing gently to distribute everything evenly. Taste and adjust the seasoning with additional salt and pepper if needed.
Take two-thirds of the filo pastry sheets and use them to line the bottom and sides of your cake pan. Brush each sheet generously with melted butter as you layer them, letting the edges overhang the rim of the pan—these will fold over the filling later. Spoon the eggplant and lentil mixture into the lined pan, spreading it evenly. Fold the overhanging filo sheets over the top of the filling to partially enclose it. Brush the remaining filo sheets with butter, then gently crumple them with your hands and arrange them artistically on top of the pie for a rustic, textured appearance.
Place the pan in the preheated oven and bake for 40 minutes or until the pastry turns a beautiful golden brown and becomes crisp. Remove from the oven and let it rest for a few minutes before slicing. Serve hot with a fresh mixed-greens salad on the side.
