In a saucepan combine 1 cup picante sauce, chicken, onion, cumin, chilli powder and salt. Cook over medium-low heat, stirring often, about 15 minutes or until most of the liquid evaporates. Taste and adjust seasoning, if needed.
Preheat the oven to 200°C and lightly grease a baking sheet.
Spoon 1/3 cup mixture below centre of each tortilla; top with about 2 tbsp cheese.
Fold in 2 sides of tortillas to enclose filling. Fold over top and bottom edges of tortillas, making rectangles. Secure with wooden picks, if needed. Place, folded-side down, on greased baking sheets. Coat chimichangas with cooking spray or brush lightly with canola oil.
Bake for 8 minutes; turn and bake 5 more minutes. Remove picks if you used them. Serve chimichangas with remaining picante sauce and desired toppings.