Preheat the oven to 350 F
In a large saucepan, heat 1 tsp of olive oil. For a fat-free option, heat 2 tbsp of vegetable stock instead.
Add the diced onions and garlic and saute for a few minutes, until the onions start to brown.
Add the tomatoes, green pepper, cilantro, coriander powder, cumin powder and chipotle chili. Mix well and cook for about 10 minutes or until the liquid has evaporated and the tomatoes look darker and caramelized.
Drain the lentils of all cooking water and add to the pan. Mix well. Cook, stirring frequently, for another five minutes at least to let all the flavors mix. Your filling should be rather dry or it will bleed out of the seams when you bake your chimichangas.
Add the lime juice and salt and set aside to cool.
Place the filo sheets on the countertop and cover with a kitchen towel. Filo dries up very fast, so you need to keep it covered at all times and work fast.
Place a sheet of the pastry on the countertop and brush lightly with oil. Layer on a second sheet, brush with oil, and finally a third sheet. Brush on a little oil and then cut the assembled sheets into four pieces by making one horizontal cut through the center and then one vertical cut.
Place some stuffing close to the corner of one of the filo rectangles. Fold in the horizontal sides over the filling and then roll to make a cylindrical shape. Place seam side down on a lightly oiled baking sheet.
Repeat for all remaining pastry sheets. You will get 12 chimichangas.
Place in the hot oven and bake 25 minutes or until golden-brown. Remove to a rack immediately, using a pair of tongs or a spatula.